This is an example of the rendering issues in Firefox (tested against 3.5.2).

When we wrap the block content with a link, if Firefox encounters a nested section element, Firefox closes all the open elements, and moves the contents outside, which causes the entire DOM to change structure.

The first example is a reference example showing how it should work with a div element. The following two are examples using section elements, both have been modified by the parsing engine in Firefox.

The correct output should have a white background against all the content.

h2 nested in a div wrapped in a link

p nested in a section wrapped in a link

h2 nested in a section wrapped in a link

The a element with a nested section element causes Firefox to trigger it's own rendering, cause the DOM to be reordered incorrectly.

In this example, all the content should be sitting on the white background.