Ok then, not generally a person to double post but I'd like to just finish off this thread with a pointer that Firefox is so insanely worthless. I decided I'd try the Tooltip approach, I sorted it out so they were the right size, wouldn't come off the margin, wouldn't do anything wrong, would be good little boxes. But no - Firefox decided it would add the padding to the width of the boxes! So in Internet Explorer, I get the right size, in Firefox, I get another that goes over the page and stretches it! What is the point of that, seriously? It makes no sense.

Regardless to say I have changed my original lovely vision in order to fit with a rendering engine that is to quote a well known film 'without meaning or purpose'. The world was fine without Firefox before, it would be fine without it now.

EDIT:

Ok, I managed to fix it. What I apparently did not realise was that for some strange I frankly stupid reason Firefox widths are content widths, not actual widths. They do not seem to include margins or padding! What is the point in that?! How does that help design? Once I worked out how to fix it in Firefox, I had managed to ruin it in Internet Explorer. It took me a whole ten minutes to make it to it didn't for Internet Explorer, and it did for Firefox.

If somebody has a good reason to set width by inner size rather than outer size, I would be grateful to hear!