I've two floating div sections on all web pages - the left contains the menu, the right displays the content - both have their fixed pixel widths specified in the stylesheet.
Pages are displayed OK on most browsers - problem is with IE 5.x on Macs - unfortunately results are not consistent - mostly the containers are displayed side by side as required - on a few pages however, the content section is displayed below the menu for no apparent reason.
The content divs only contain text within 'p' tags with no other formatting - it's as if some paragraphs are forcing a greater width on these odd occasions - it's got me stumped!
Floating Divs in IE 5.1 Mac
The content in the content section may be expanding the div.
Have you tried playing with overflow values to see what happens.
Hope that helps