W3C home > Mailing lists > Public > www-style@w3.org > May 2004

Re: CSS: Extended tiling. Proposal

From: David Woolley <david@djwhome.demon.co.uk>
Date: Thu, 6 May 2004 12:30:02 +0100 (BST)
Message-Id: <200405061130.i46BU2f10132@djwhome.demon.co.uk>
To: www-style@w3.org

> UA needs to send at least header request to the server and it is again those
> 40k.

Please give an example of a 40 KB header.  A typical request header,
ought to be:

GET /images/spacer.gif HTTP/1.1
Host: www.example.com
Accept: ..... about 60 bytes? ......
Accept-Language: en-gb, en
User-Agent: user-agent/9.9 (about 40 bytes of comments)
Referer: http://www.example.com/index.html

The request header can be pipelined and need have no impact on throughput,
after the first.

An actual, non-minimal (involves language negotiation which most sites 
don't use, and even fewer use for images) response header is:

HTTP/1.1 200 OK
Date: Thu, 06 May 2004 11:11:07 GMT
Server: Apache/1.3.20 (Unix)
Content-Location: index.html.en
Vary: negotiate,accept-language,accept-charset
TCN: choice
Last-Modified: Fri, 04 May 2001 00:00:38 GMT
ETag: "4180a-5b0-3af1f126;3c3a2b2f"
Accept-Ranges: bytes
Content-Length: 1456
Connection: close
Content-Type: text/html
Content-Language: en
Expires: Thu, 06 May 2004 11:11:07 GMT

That's just over 400 bytes, so the total overhead, assuming that the
browser cache doesn't satisfy the request, and even mobile phones cache,
is about 750 KB, of which only about 400 is not overlapped.
Note that these will get compressed over a modem connection.

> Yep! And would you want to see also that not only images but borders will
> appear one by one?

What I want is for enough of the page to appear within 5 to 10 seconds
on a 33kb connection that I can continue navigating or read the first
screenful of content.  If the author uses image replacement and doesn't
provide good alternative text (or I'm using a browser that doesn't handle
alternative text particular well), the only hope I have of being able to
use that page efficiently is if the images are displayed as they arrive;
if I'm lucky, the text for the button that I want will appear sooner, rather
than later.

If, as sometimes happens because of multiple images and the use of layout
tables without fixed layout styling, a page stays completely blank for 
30 seconds, I'll normally assume that this is because of an abuse of scripting
and go elsewhere.

Unless I was going to print the page for someone else, the only thing that
I would care about the borders is that they didn't get sent until after
all the substantive content had arrived.  As a user of the page, I really
couldn't care about whether they are displayed incrementally or all at
once, as long as they don't delay the real information.

While it is true that a good author will make the text work in its own right,
whilst waiting for the image package, as you yourself pointed out, few 
page designers understand how to use the technology properly, and even if
they do, their clients probably will object to the delay in the presentation
of the page branding until all the images are available.
Received on Thursday, 6 May 2004 14:54:05 UTC

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