I finally got my whole layout work with percentages.

Now there's one problem: the two columns are unevenly long.

That will always be the case, as there is never a balance in amount of content in both.

So I'd like to define the length of the columns independently from their content.

Is there a way to do this? By using height? 100%? How?

Comments appreciated.

Vertically tiled background that fakes equal column length.

Could this be the best solution?

http://www.alistapart.com/articles/fauxcolumns/

Yes, that is the simplest and probably the best solution. Works like a charm