W3C home > Mailing lists > Public > www-style@w3.org > June 2000

Re: positioning elements and left,right,bottom,top

From: Matthew Brealey <webmaster@richinstyle.com>
Date: Mon, 19 Jun 2000 09:01:37 -0700
Message-ID: <394E43E1.F90@richinstyle.com>
To: www-style@w3.org
fantasai wrote:
>    (Since the margins are auto, they will stretch
>     to fill the space between the box defined by
>     the positioning properties and the borderline
>     of the positioned element.)

Well, no they're not actually. Which can cause problems
('over-constrainment'): see for example the fixed positioning example in
the spec.

It is, under the published specification at least, necessary to set
margins explicitly to auto. An example of such a case is when height,
top and bottom have all been set, and margin-top is (usually implicitly)
0: the fact that height + top + bottom + margin-top (+ margin-bottom,
but this is usually irrelevant) must equal the height of the containing
block; the problem being that to rectify this, margin-top is not
ignored, so you must explicitly in such cases specify margin-top: auto.
There is an analogous case for horizontal dimensions.

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Received on Monday, 19 June 2000 03:55:12 UTC

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