I ran into a problem with FireFox where it would not display images properly in a table.  The image would float to the top of a cell and always have several pixels add to the botom regardless of the cell height specified.

After a bit of digging, I found this was a problem when I used a "strict" document type and not when in "transitional".  I still wanted to use "strict" (even though the actual content did was not 100% strict compliant) as it forced Internet Explorer to handle some other issues of compatibility I had, so that was not an option.

After yet even more research, I found that it appears FireFox and Safari both default image vertical alignment to "baseline" in "strict" mode.  By simply setting:

img
{
vertical-align: top;
}

This solved the problem for my site.