W3C home > Mailing lists > Public > www-style@w3.org > January 2008

Re: positioned elements: center

From: David Woolley <forums@david-woolley.me.uk>
Date: Tue, 08 Jan 2008 22:44:53 +0000
Message-ID: <4783FCE5.10209@david-woolley.me.uk>
To: CSS Style <www-style@w3.org>

Andrew Fedoniouk wrote:

> If you want to center something in the view then you
> will prepare block that will (usually) fit in the view in the whole.
> Thus, it is highly probable that your document will be contained
> in the very first http buffer (4k or so) in the whole.

The optimum TCP segment size on WANs is slightly less than 1500 bytes 
and modern software should be using path MTU discovery to ensure this is 
achieved.  On the other hand, yahoo.co.uk's home page is 100K.  Almost 
half of this is the embedded style sheet, and it is a bit difficult to 
separate scripting from content.  (Note, whilst your web browser may 
supply 4K buffers for its network reads, the typical kernel support for 
TCP will return control when it runs out of available segments, even if 
there is buffer space left.)

Whilst good use of HTML, CSS, and external style and script files can 
reduce the size of documents from competent authors, I'm more concerned 
about the majority of documents, which are also likely to have a lot of 
bloat from inline styling.  A TCP segment is likely to be small compared 
with many home pages.

My concern with vertical centering arises partly from what happened when 
the CENTER element was first introduced.  Ignoring my opinions about the 
bad effect this has had on web page readability, the point is that it 
illustrates that web authors love centering.  I suspect, therefore that 
an easy to use vertical centering mechanism will get heavily used.

That leaves the question of whether people will only use it for small 
items that can reasonably have their rendering deferred.  My guess is 
that most people will use it that way, but I still think a quite large 
number will use it to centre the main part of their homepage.  Typically 
people try and get the home page onto one screen but they also often try 
and cram large amounts on it (one of the reason for the font size 
usability problems)

As to the question of not implementing what people want, there is a long 
tradition of that in W3C.  I'd argue that CSS itself wouldn't have 
existed without that, but other examples are the lack of frames, font, 
etc. in strict versions of HTML, and the making of alt attributes mandatory.

David Woolley
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Received on Tuesday, 8 January 2008 22:45:24 UTC

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