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Archive-name: www/stylesheets/authoring-faq
Posting-Frequency: twice a week (Mondays and Thursdays)
Last-modified: August 28, 2002
Version: 1.15
URL: http://css.nu/faq/ciwas-aFAQ.html
Maintainer: Jan Roland Eriksson <rex@css.nu>
ciwas stylesheet authoring FAQ v1.15
______________________________________________________________________
The Purpose, Scope and Notation of this FAQ-list.
This FAQ-list contains the edited result of a collective effort among
regular participants in the Usenet newsgroup...
comp.infosystems.www.authoring.stylesheets
The purpose of this document is to provide answers to a few of the
most frequent questions raised in the 'ciwas' Usenet newsgroup.
At the moment, almost all discussion on this group relates to CSS,
although that might not always be so. This document does not aim to be
a complete tutorial in stylesheets or in CSS.
There is a separate FAQ-list about the Usenet group itself, its
charter, customs and posting conventions. For further information
about stylesheets and about CSS see the resources listed in the
resource sections of http://css.nu/faq/ciwas-mFAQ.html
The following notational convention is used in this FAQ.
Single quote marks are used to denote keywords,
e.g. 'font-family'
and those quote marks are not a part of the keyword.
Double quote marks are used to denote text that is quoted from
another source, and/or to mark jargon.
e.g. "Generic font family names are keywords..."
would indicate that the line contains quoted material.
Stars denote emphasized text...
e.g. *not*
would put emphasis on the word "not".
______________________________________________________________________
00: ===== T O C =====
01: I want my page fonts to look the same every where as in...
a) Why are my font sizes different in different browsers ?
b) Why are my font sizes different on different platforms ?
02: Why shouldn't I use fixed sized fonts ?
03: Which font names are available on all platforms ?
04: How can I make a page look the same in e.g. NS and MSIE ?
05: Why is my external stylesheet not working ?
06: Why does Netscape lose my styles ?
07: How does a simple CSS style rule look ?
08: How can I suggest a different link appearance in various sections
of my page ?
09: Why is it my ':hover' declaration for links does not work ?
10: Where can I learn more about CSS ?
11: How can I check my CSS creations and find out about errors ?
12: What is this thing I hear about <!DOCTYPE... declarations ?
13: Where can I find the latest version of this FAQ ?
14: Is this FAQ available in other languages ?
______________________________________________________________________
01: ===== Q & A =====
Q: I want my page fonts to look the same everywhere as in...
a) Why are my font sizes different in different browsers ?
b) Why are my font sizes different on different platforms ?
A: These questions represent the tip of the iceberg of a large topic
about which whole essays have been written and a wide range of
different views are held.
The WWW was originally devised to present the same *content* in
different presentation situations and for a wide range of readers:
on that basis, "looking the same" is not a design criterion,
indeed different presentations would be *expected* to look
different.
Some would have it that this original aim is no longer relevant,
and that the purpose of web design is now to factor out the
differences between display situations and put the author in
control of the details of the presentation. Others point out that
CSS was designed to give the reader a substantial amount of joint
control over this process, and that this is desirable, for example
to accommodate users with different visual acuity.
Reading of textual matter on a computer screen is quite a
delicate business, what with the relatively coarse pixel structure
of a computer display; even with a close knowledge of the display
details, it isn't possible to achieve the detailed control that
would be possible, say, on a printer. Whatever one's aims, the
practical truth is that many of the efforts made to guarantee the
precise result on the screen have seriously counterproductive side
effects in a www situation.
The CSS specifications themselves recommend that authors should
not use absolute size units in a situation where the properties of
the display are unknown. There's a lot to be said for flexible
design, that in an appropriate situation looks the way you had in
mind, but still successfully conveys content and message in a wide
range of other browsing situations.
And so, before looking at the technical detail of what can be
specified, it's strongly suggested that you read some of those
essays on web design, and reach your own conclusions as to
the strengths and weaknesses of the medium, and how you can best
exploit the strengths in a web environment, without falling foul
of the weaknesses.
Suggested reading material...
http://style.cleverchimp.com/
http://www.westciv.com/style_master/house/good_oil/not_paper/
02: ===== Q & A =====
Q: Why shouldn't I use fixed sized fonts ?
A: Only in very rare situations we will find users that have a
"calibrated" rendering device that shows fixed font sizes correct.
This tells us that we can *never* know the *real* size of a font
when it's rendered on the user end.
Other people may find your choice of font size uncomfortable.
A surprisingly large number of people have vision problems and
require larger text than the average. Other people have good
eyesight and prefer the advantage of more text on the screen that
a smaller font size allows. What is comfortable to you on your
system may be uncomfortable to someone else.
Browsers have a default size for fonts. If a user finds this
inappropriate, they can change it to something they prefer.
You can never assume that your choice is better for them. So,
leave the font size alone for the majority of your text. If you
wish to change it in specific places (say smaller text for a
copyright notice at the bottom of page), use relative units so
that the size will stay in relationship to what the user may have
selected already.
Remember, if people find your text uncomfortable, they will not
bother struggling with your web site. Very few (if any) web sites
are important enough to the average user to justify fighting with
the author's idea of what is best.
Suggested reading material...
http://css.nu/articles/font-analogy.html
See also Q & A - 01: above.
03: ===== Q & A =====
Q: Which font names are available on all platforms ?
A: The simple answer is "None" which is why CSS offers five generic
font names as 'serif', 'sans-serif', 'cursive', 'fantasy' and
'monospace'. Never put any of these generic font names in quotes.
A CSS aware browser should make a suitable choice from the
available fonts in response to each of those generic names.
Specifying any other font name in a www environment comes out as
a *suggestion* only, that may or may not be acknowledged by a
browser.
The problem with using names of specific fonts is that there is
little point in naming fonts that few users will have, so you're
down to listing a few mass-market font names. This will then
override any superior selection that a minority of discerning
readers may have made for themselves.
Note also that fonts may differ in their character repertoire,
but this is often not evident from the font name itself:
by selecting an inappropriate font name, you might prevent
internationalized content from displaying correctly for a
proportion of users.
Also beware of the fact that MSIE on Windows platforms has a few
bugs in the font selection area, as described here...
http://css.nu/pointers/bugs.html
For more details on the 'font-family' property, see...
Section 5.2.2 "font-family" in the CSS1 specification...
http://www.w3.org/TR/REC-CSS1#font-family
04: ===== Q & A =====
Q: How can I make a page look the same in e.g. NS and MSIE ?
A: The simple answer is, you can't, and you shouldn't waste your time
trying to make it *exactly* the same. Web browsers are allowed,
per definition, to interpret a page as they like, subject to the
general rules set down in the HTML and CSS specifications.
As a web author you can not have a prior knowledge of the exact
situation and/or medium that will be used to render your page, and
it's almost always rather counterproductive to try to control that
process.
There is no necessity for a well-written page to look the same in
different browsers. You may want to strive to ensure that it looks
*good* in more than one browser, even if the actual display (in
the case of graphical browsers) comes out a bit different.
"Looking good" can be achieved by adopting sensible design and
guidelines, such as not fixing the size or face of your fonts, not
fixing the width of tables, etc...
Don't fight the medium; most web users only use one browser and
will never know, or bother to find out, that your page looks
different, or even "better", in any other browser.
So accept that the flexibility built into the www medium is your
friend and just make sure that users can get at your content in an
easy way, and design your pages accordingly.
05: ===== Q & A =====
Q: Why is my external stylesheet not working ?
A: There may be several different reasons behind that, but one very
common mistake is to have an external stylesheet that contains
HTML markup in some form.
An external stylesheet must contain *only* CSS rules, and if
required, correctly formed CSS comments; *never* include any HTML
syntax, such as <style type="text/css">...</style>, in your
external stylesheets.
CSS comments are defined as anything that is placed between
/* (the comment start mark) and
*/ (the comment end mark). I.e. as follows...
/* This text right here is a correct CSS comment */
CSS comments may span multiple lines in the stylesheet.
Nesting of CSS comments is *not* allowed.
Another reason for external stylesheets (and even embedded and
inline stylerules) not to function as expected may be that you
have tried to make use of some CSS-features that are not supported
in the browser you are using.
Browser support for CSS varies and a good place to find out more
about what is or is not supported is "The Mastergrid"...
http://www.webreview.com/style/css1/charts/mastergrid.shtml
External stylesheets shall also be served from the www-server with
a MIME-type of 'text/css' in its 'Content Type:' HTTP header.
You may need to negotiate with your server admin to add this
MIME type to your server if you are not able to configure the
server yourself.
Registered MIME types can be found in the IANA repository...
ftp://ftp.isi.edu/in-notes/iana/assignments/media-types/
RFC2318 describes the specific 'text/css' MIME type.
http://www.ietf.org/rfc/rfc2318.txt
HTTP header content for www resources may be checked here...
http://www.rexswain.com/httpview.html
http://www.delorie.com/web/headers.html
http://www.webmastermatrix.com/webtools/HTTP%20Header%20Viewer.htm
06: ===== Q & A =====
Q: Why does Netscape lose my styles ?
A: Netscape 4.x has poor support for CSS. Having said that, the
following points should be noted.
Invalid HTML will almost certainly cause Netscape to ignore your
CSS suggestions at some point. You will find that valid HTML is
your best friend, but for Netscape to work properly you must
ensure that *all* elements in your markup which permit closing
tags are explicitly closed.
Check and correct your CSS suggestions for the very same reason,
Netscape 4.x is in fact doing "the right thing", as per CSS specs
(as opposed to MSIE) when it ignores style rules with errors.
Netscape 4.x has what's called an "inheritance problem" into its
TABLE element. It can be argued that NS is all within its right to
behave as it does in this case, but since the workaround is quite
simple it's easy enough to just use it and be done with it.
Let's say you want your TABLE content to "look the same" as your
BODY content? "Redundant" styling comes to your help as in e.g.
BODY, TABLE, TH, TD { /* insert your styles here */ }
On a generic level, Netscape 4.x likes to have style rules applied
directly to the elements where they are needed. You can never
really trust the inheritance principle to work correctly at any
level in Netscape 4.x.
See... http://css.nu/pointers/bugs.html for more details of bugs
and workarounds in Netscape's CSS support.
A good method to limit the influence of CSS in the Netscape 4.x
family of browsers is to make use of the '@import' trick to serve
only such levels of CSS to Netscape 4.x that it can cope with.
Johannes Koch describes svereal methods that can be used to
isolate certain browsers from CSS rules that are supported less
than good...
http://pixels.pixelpark.com/~koch/hide_css_from_browsers/
07: ===== Q & A =====
Q: How does a simple CSS style rule look ?
A: P { font-family: serif; font-size: 1.2em; }
Here we see a rule with a 'selector' P that has been given two
style declarations, i.e. two 'property:value' pairs.
'font-family' and 'font-size' are properties of the content of
element P, and these properties are assigned the values of 'serif'
and '1.2em' respectively.
A colon ':' is the *value assignment symbol* in CSS, so using an
equal sign '=' instead is an *error* and is required by the CSS
specification to be ignored. Any browser that appears to honor
this style is behaving improperly.
For length values a 'unit' is always needed and there shall
*never* be any space between a number and its length unit.
A value given as e.g. '1.2 em' is an *error* and is required by
the CSS specification to be ignored. Any browser that appears to
honor this style is behaving improperly.
A semicolon ';' *between* declarations is required but it's also
good "rule of thumb" to put a ';' even after the last declaration.
Finally, curly braces '{...}' group one or more declarations into
a final CSS rule.
For more details on the basics of CSS style rules,
see Section 1 "Basic concepts" in the CSS1 specification...
http://www.w3.org/TR/REC-CSS1#basic-concepts
08: ===== Q & A =====
Q: How can I suggest a different link appearance in various sections
of my page ?
A: The most direct approach is to define separate classes for your
link types and then use those classes directly in your <a href=...
markup. The following is a simple example based on info from the
CSS2 specification sections 5.11.2 and 5.11.3.
http://www.w3.org/TR/REC-CSS2/selector.html#link-pseudo-classes
http://www.w3.org/TR/REC-CSS2/selector.html#dynamic-pseudo-classes
a.internal:link { background: #c0c0c0; color: #800080; }
a.internal:visited { background: #c0c0c0; color: #008080; }
a.internal:hover { background: #c0c0c0; color: #00ffff; }
a.internal:active { background: #c0c0c0; color: #008000; }
a.external:link { background: #ffffff; color: #ff0000; }
a.external:visited { background: #ffffff; color: #0000ff; }
a.external:hover { background: #ffffff; color: #ffff00; }
a.external:active { background: #ffffff; color: #00ff00; }
And in your markup you can then use...
<a class="internal" href="#foo">Link to Foo</a>
<a class="external" href="http://bar.baz">Link to Bar</a>
...to suggest a difference in appearance for what could be your
internal or external links. Most CSS properties are available for
setting up style rules for links and the example above is kept to
a minimum only to save space.
Also note that the grammatic rules for CSS1 only allows for this
following link selector format to be used...
a.internal:link { background: #c0c0c0; color: #800080; }
...while the grammar for CSS2 allows for both of these...
a.internal:link { background: #c0c0c0; color: #800080; }
a:link.internal { background: #c0c0c0; color: #800080; }
Since support for the CSS1 syntax is more wide spread, it is
advised that you only use CSS1 syntax for your link style rules.
09: ===== Q & A =====
Q: Why is it my ':hover' declaration for links does not work ?
A: Assuming you have already checked that your style sheet
declarations do conform to correct CSS syntax, it could be that
you have overlooked the importance of a correct order of style
declarations for links.
The CSS2 specification makes this following note on the importance
of placing the dynamic pseudo-classes ':hover' and ':active' in
correct positions in a list of style declarations.
"Note that the 'a:hover' must be placed after the 'a:link' and
'a:visited' rules, since otherwise the cascading rules will hide
the 'color' property of the 'a:hover' rule. Similarly, because
'a:active' is placed after 'a:hover', the active color will apply
when the user both activates and hovers over the 'a' element."
See also Q & A - 08: above for an example of correct ordering of
link style declarations, and further, for the full theory, see
these parts of the CSS2 spec.
http://www.w3.org/TR/REC-CSS2/selector.html#link-pseudo-classes
http://www.w3.org/TR/REC-CSS2/selector.html#dynamic-pseudo-classes
Note that the ':hover' pseudo-class entered into CSS specs in CSS2.
Browsers that do not claim to support CSS2 at any level, can not be
expected to support the ':hover' pseudo-class. E.g. Netscape 4.x
and Opera 3.x browsers does not have support for the ':hover'
pseudo-class.
10: ===== Q & A =====
Q: Where can I learn more about CSS ?
A: The meta-FAQ for comp.infosystems.www.authoring.stylesheets has a
resource section that lists a large number of URL's to www-sites
that are know to contain good information on how to use and author
Cascading Style Sheets (i.e. CSS for short).
The meta-FAQ is posted here in this NG with the same frequency
as this FAQ, but can also be found on the www as an HTML document.
http://css.nu/faq/ciwas-mFAQ.html
...or as a plain text document...
http://css.nu/faq/ciwas-mFAQ.txt
11: ===== Q & A =====
Q: How can I check my CSS creations and find out about errors ?
A: For traditional markup syntax validation...
http://www.htmlhelp.org/tools/validator/
http://valet.webthing.com/page/
http://validator.w3.org/
For CSS check-ups...
http://www.htmlhelp.org/tools/csscheck/
http://jigsaw.w3.org/css-validator/validator.html.en
Make friends with the URL's above, they *will* save you a lot of
time and frustration. To emphasize this point, *overly* correct
HTML markup -- I.e. explicitly closing elements which do not
strictly require this -- and correct use of CSS, is essential to
ensure properly rendered CSS on the www.
The validator located at webthing.com (The Page Valet, URL above)
has an experimental "normalised markup" option that makes use of
"spam" (SPAddMarkup) to insert, among other things, the optional
closing tags. "The Page Valet" is based on exactly the same code
and error messages as is used for the validator at htmlhelp.org
"To err is human", but for once there is something that computers
can help out with: *error checking*. Just like spell checkers may
catch irritating typos that are so hard to spot by eye, HTML
validators and CSS checkers are available on-line to check your
web pages (URL's above).
You will need to use your knowledge of HTML and CSS to interpret
the results of these tools, but you can post follow-up questions
to this NG, comp.infosystems.www.authoring.stylesheets for further
discussion.
12: ===== Q & A =====
Q: What is this thing I hear about <!DOCTYPE... declarations ?
A: A couple of popular www browsers have been programmed to contain
more than one document rendering mode, one mode that is designed
to mimic old browsers rendering behavior and another mode that is
designed to follow avilable CSS recommendations as best possible.
The former is usually refered to as "quirks" mode and the latter
as "strict" (or "standard") rendering mode.
These browsers makes use of a specific entry in the document
prologue named 'DOCTYPE' declaration and inspects the content of
such a declaration to decide on how to proceed with the rendering
phase for a document.[a]
Browsers that are not designed to do "<!DOCTYPE... sniffing" will
not be affected by the inclusion of a 'DOCTYPE' declaration, so
from a CSS point of view, you can always include a declaration
that makes sense for the rendering mode you want to suggest.
The following is valid for (X)HTML documents served with a
'Content-Type: text/html' in their HTTP document headers.
For HTML 4.01 you should be safe to use this declaration in your
document prologue if your target is to suggest activation of the
"strict" rendering mode in browsers that makes use of
"<!DOCTYPE... sniffing"
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
For XHTML 1.0 this following declaration should be safe in your
prologue for the purpose of suggesting a "strict" rendering mode.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
For additional information on the full span of variations that
came as a result of the introduction of "<!DOCTYPE... sniffing",
please consult the following www resources.
http://gutfeldt.ch/matthias/articles/doctypeswitch.html
http://www.hut.fi/u/hsivonen/doctype.html
http://world.std.com/~mmcirvin/mypages.html#doctype
http://www.mozilla.org/docs/web-developer/quirks/doctypes.html
[a] The concept of a 'DOCTYPE' declaration has its roots in the SGML
standard and is used there for a completely different purpose.
A description of that original use of a 'DOCTYPE' declaration is
considered to be outside the scope of this FAQ-list.
13: ===== Q & A =====
Q: Where can I find the latest version of this FAQ ?
A: This FAQ was last updated 2002/08/28 copyright 2000, 2001, 2002
-- Jan Roland Eriksson.
Permission to freely reproduce this document electronically is
given as long as the document remains uncut and unedited.
This FAQ is posted periodically to the NG every Monday and
Thursday and I'll endeavor to use the same subject line at all
times so that those of you who have seen it can kill-file the
subject.
FAQ version number in subject line will be changed whenever the
document has been revised. You should be able to use that fact
when setting your kill filter to make sure that you have the
latest version available at all times.
This FAQ is also available in HTML on the World Wide Web;
at... http://css.nu/faq/ciwas-aFAQ.html
...and as a text document;
at... http://css.nu/faq/ciwas-aFAQ.txt
...with the revision history of this FAQ;
at... http://css.nu/faq/ciwas-aFAQ-rev.html
14: ===== Q & A =====
Q: Is this FAQ available in other languages ?
A: Matthias Gutfeldt maintains a German translation of this
original FAQ-list on the www at...
http://gutfeldt.ch/matthias/translation/css_faq/ciwas-aFAQ.html
Rijk van Geijtenbeek maintains a Dutch translation of this
original FAQ-list on the www at...
http://rijk.op.het.net/info/niwo/ciwas/ciwas-aFAQ.html
15: ===== E N D =====
______________________________________________________________________
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