Cross browser method to fit a child div to its parent's width

问题

I'm looking for a solution to fit a child div into it's parent's width.

Most solutions I've seen here are not cross-browser compatible (eg. display: table-cell; isn't supported in IE <=8).

回答1:

The solution is to simply not declare width: 100%.

The default is width: auto, which for block-level elements (such as div), will take the "full space" available anyway (different to how width: 100% does it).

See: http://jsfiddle.net/U7PhY/2/

Just in case it's not already clear from my answer: just don't set a width on the child div.

You might instead be interested in box-sizing: border-box.

回答2:

You can use box-sizing css property, it's crossbrowser(ie8+, and all real browsers) and pretty good solution for such cases:

#childDiv{
   box-sizing: border-box;
   width: 100%; //or any percentage width you want
   padding: 50px;
}

Fiddle

回答3:

In your image you've putting the padding outside the child. This is not the case. Padding adds to the width of an element, so if you add padding and give it a width of 100% it will have a width of 100% + padding. In order to what you are wanting you just need to either add padding to the parent div, or add a margin to the inner div. Because divs are block-level elements they will automatically expand to the width of their parent.

回答4:

If you put position:relative; on the outer element, the inner element will place itself according to this one. Then a width:auto; on the inner element will be the same as the width of the outer.