CSS is not the 'Alpha and Omega' of presentation. In addition to Pure CSS Popups, there are also many solutions based on JS that work cross-broswer, work right 'out of the box', are very compact in code, and have a significant range of funcutionality. Probably 95%+ of your users will have JS enabled. Keep your options open.
Tables were hacked every which way to make pages do what authors wanted. CSS has seen the same. There is nothing wrong with that. Just don't forget that the designer's toolbox has all kinds of useful stuff in it.