W3C home > Mailing lists > Public > public-html@w3.org > July 2007

Re: HTML 5 proposal - OBJECT elements, environment discovery and alternative content

From: Kornel Lesinski <kornel@geekhood.net>
Date: Tue, 31 Jul 2007 20:51:15 +0100
To: "Philip Ronan" <philronan@blueyonder.co.uk>
Cc: "public-html@w3.org" <public-html@w3.org>
Message-ID: <op.twchfpooptj49s@g5.local>

On Tue, 31 Jul 2007 18:22:41 +0100, Philip Ronan  
<philronan@blueyonder.co.uk> wrote:

> (1) A web page providing instructions on how to download an image might  
> contain the following:

You could use Content-Disposition header and simply link to an image.

> (2) A web page that contains a few characters of Japanese will not  
> display correctly

IMHO a better approach would be to embed a custom font that contains these  
characters and set it as last alternative in CSS.

> (3) A website with user-selectable CSS stylesheets could use a cookie to  
> store the client's preferred style and set this stylesheet as the  
> default stylesheet for subsequent page views.

I think this would be better solved if UAs simply remembered user's choice  
of alternate stylesheet.

However for this and similar customizations, you could use HTML5's  
client-side storage:
http://www.whatwg.org/specs/web-apps/current-work/multipage/section-storage.html

> According to the HTTP specification (RFC2616), content that varies in  
> this way should include a Vary header. So in case (1), the server should  
> flag the page with the HTTP header "Vary: User-Agent". Unfortunately,  
> this would make it almost pointless caching the content

Although Vary header doesn't work, it's not the only possible way. You can  
use Cache-control: private to avoid polluting public caches with  
customized pages and use E-tag for cache validation of different versions.

> <OBJECT selector="User-Agent" match="Macintosh">
> Click on the image while holding down the <B>Control</B> key,

The problem is, there are a lot more platforms and browsers than average  
webmaster could even name (including  
"Macintosh-that-supports-right-mouse-button" ;) and it would be nearly  
impossible to support them all in that way.

A different, platform-agnostic approach would be easier for webmasters and  
better for users of OS/browser combinations that aren't in top 2.
If instructions for saving an image were important, it could be <img  
for-saving> or <help show="how-to-save-an-image">.

-- 
regards, Kornel Lesinski
Received on Tuesday, 31 July 2007 19:51:35 UTC

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