Ok so anyway I did this, using the code posted above:
See the form is sticking out in both FF and IE7.
Now the broadest width I can get away with is 275px on section div. 276px, IE7 wraps.
Now, this only happens in IE7... when the margin-right: 45px is a margin.
Change it to padding-right. Suddenly, Firefox is just as intolerant as IE7.
This tells me that some child (and I'm strongly suspecting the form) is making that last div wider than you think in IE7. When we use padding, this is added to the total width of the box itself, so 275+45=320px.
When we use margin, the total width of the box is still 270px, but the amount of space it claims for itself is +45px = 320px. But I'm thinking somehow a wider child is being counted in IE7, meaning that last box is 45px margin + 275px + something from a child stretching the width of that box.
I'd just make the inputs less wide.
And I'd ditch the tranny doctype, I dunno what that's doing in there... (has nothing to do with this problem tho)