Why is box-sizing acting different on table vs div?
css, html, html-table
Solution
Yes, CSS2.1 states the following for tables with the separated borders model:
However, in HTML and XHTML1, the width of the <table> element is the distance from the left border edge to the right border edge.
Note: In CSS3 this peculiar requirement will be defined in terms of UA style sheet rules and the 'box-sizing' property.
The current CSS3 definition of `box-sizing` does not say anything about this, but translating the above quote it basically means in (X)HTML, tables use the border-box model: padding and borders do not add to the specified width of a table.
Note that in terms of the `box-sizing` property, different browsers seem to handle this special case differently:
Chrome `box-sizing` is set to the initial value, `content-box`; changing it has no effect whatsoever. Neither does redeclaring `box-sizing: content-box` within the inline styles, but that should be expected. Either way, Chrome appears to be forcing the table to always use the border-box model.
IE `box-sizing` is set to `border-box`; changing it to `content-box` causes it to behave like the second `div`.
Firefox `-moz-box-sizing` is set to `border-box`; changing it to `content-box` or `padding-box` causes it to resize accordingly.
Since CSS3 does not yet make any mention of table box sizing, this should not come as a surprise. At the very least, the result is the same — it's only the underlying implementation that's different. But given what the note says above, I would say that IE and Firefox are closer to the intended CSS3 definition, since in Chrome you can't seem to change a table's box model using the `box-sizing` property.
Tables with the collapsing border model don't have padding at all, although in this case it's not relevant since your table does not use this model:
Note that in this model, the width of the table includes half the table border. Also, in this model, a table does not have padding (but does have margins).
Problem
Here's the HTML: http://jsfiddle.net/jC8DL/1/ ``` <div style='width:300px;border:1px solid green'> <div>Outer div</div> <div style='width:100%;border:1px solid red;margin:10px;'> Inner div, 10px margin. </div> <div style='width:100%;border:1px solid red;padding:10px;'> Inner div, 10px padding. </div> <div style='width:100%;border:1px solid red;padding:10px;box-sizing:border-box'> Same, with box-sizing: border-box </div> <table style='width:100%;border:1px solid red;padding:10px;'> <tr><td>Inner table, 10px padding</td></tr> </table> </div> ``` And it looks like this in my Chrome: I think I understand everything until the last one. My Chrome inspector shows the table's computed `box-sizing` style is `content-box` so I expect it to behave like the second div, and overflow and look ugly. Why is it different? Is this documented somewhere in the HTML/CSS spec?