This presentation is best viewed in a browser that supports CSS style sheets, e.g. Arena.
Web Style Sheets
Håkon W Lie
howcome@w3.org
11 Jan 96
Motivation
- HTML is structural
- authors want presentational control
- tag abuse
- new tags (CENTER, FONT), attributes (BGCOLOR)
Page check
10 W3C member front pages:
- 6/10 use background color/image
- 7/10 make images of text
- 8/10 use presentational tags
- 1/10 is according to HTML 2.0
Authors will and should be given influence.
Possible solutions
- new HTML tags
- new formats (Postscript, PDF)
- style sheets
Style Sheets
- preserve document structure, device independence
- enable rich styles: fonts, colors, spacing
- allow both author and reader influence
- lightweight
- SGML community: DSSSL (Document Sematics and Style Specification Language)
- Web community: CSS (Cascading Style Sheets)
DSSSL
- ISO standard
- 5+ years of work
- tree transformation and style sheet language
- syntax based on Scheme
- not implemented
- designed for traditional publishing model
- (scared (of (parenthesis)))
CSS
- simple, human read/writable
- based on several web style sheet proposals
- replaces all commonly used HTML extensions
- cascading resolves reader/author conflicts
- 3 implementations: Arena, emacs-w3, Tamaya
DSSSL/CSS relationship
- common goals
- different focus
- conversion possible, but lossy
- CSS specification will describe mapping
- peaceful coexistance possible
HTML-CSS
<LINK REL=STYLE HREF="style.css">
<STYLE>
H1 { font-family: helvetica }
EM { color: red }
</STYLE>
<P STYLE="background: white">
Cascading
- multiple style sheets
- multiple sources
- reader/author conflicts
- conflict resolution:
- assigned weights
- equal weight -> author wins
- legal warnings
- reader can turn style sheets on/off
Deployment issues
- fonts
- browser support
- style sheet editors
- conversion programs
- content support
- reader support
CSS workplan
oct 94: CSS first proposed
mar 95: Arena style sheets shown at WWW3
nov 95: style sheet workshop
dec 95: CSS1 -> W3C Working Draft
dec 95: Arena source under W3C copyright
jan 96: CSS1 will be submitted to IETF
apr 96: Arena fully implements CSS1
jun 96: CSS2 published as working draft
CSS2
- multiple media
- beyond HTML
- frame-based layout
- environmental influence
- expressions