kjo kjo - 6 months ago 71
CSS Question

How to disable margin-collapsing?

Is there a way to disable margin-collapsing altogether? The only solutions I've found (by the name of "uncollapsing") entail using a 1px border or 1px padding. I find this unacceptable: the extraneous pixel complicates calculations for no good reason. Is there a more reasonable way to disable this margin-collapsing?

Answer

There are two main types of margin collapse:

  • Collapsing margins between adjacent elements
  • Collapsing margins between parent and child elements

Using a padding or border will prevent collapse only in the latter case. Also, any value of overflow different from its default (visible) applied to the parent will prevent collapse. Thus, both overflow: auto and overflow: hidden will have the same effect. Perhaps the only difference when using hidden is the unintended consequence of hiding content if the parent has a fixed height.

Other properties that, once applied to the parent, can help fix this behaviour are:

  • float: left / right
  • position: absolute
  • display: inline-block

You can test all of them here: http://jsfiddle.net/XB9wX/1/.

I should add that, as usual, Internet Explorer is the exception. More specifically, in IE 7 margins do not collapse when some kind of layout is specified for the parent element, such as width.

Sources: Sitepoint's article Collapsing Margins and 960 Development's Understand CSS Margins Collapsing

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