Question

It seems like HTML5 does not support relative height of iframes. When adding

to my document height in the css rule

#content{width:100%; height:100%;border:1px solid;}

is ignored by firefox. Without the doctype, it works.

EDIT: I found that I needed to add size of html element as well. Now it works.

Answer 1

Try making the iframe’s position absolute:

#content{
    position: absolute;
    width: 100%;
    height: 100%;
    border: 1px solid;
}