I would like to know about this too.
Note : with IE 7, many things have changed in the way css are applied (thanks MS... great job !).
Because of all this, I changed all the layout and style, to make my own.
After having tried some Div structure for the layout, as it is recommended, I finally used simple table.
To have a minimum width, you can put a "special cell", not much visible, that has something in it that have the requiered width. Like a blank gif. It should prevent from reducing the TD further than this thing.
not nice, but should work.
note also : version 2.6 comes with a new layout and theme (called "renaissance"). May be interesting to look at it...
Renaissance and all the other themes use a variant of the IE hack, at least in 2.4.1. The margins are all a little different, but the same div names are used.
I can't see an appreciable difference between what I'm doing and what "Ren" is doing.