Select in a Form

I know that my question is not about Smarty, but I hope you can help me! :-) Well, I have several SELECT in a form. When I select an item in the first SELECT, some specified items are loaded in the others SELECT by javascript code. My problem is about the apparience of my web page, because this SELECT boxes are resized every time I load new items depending on strings length tha are loaded. I would like every time I load new items, SELECT boxes have a fixed size. I have tried to add space characteres to items to make they bigger until a determined size, so every item would have the same length. The problem is that these characteres are not shown in the web, are omitted. Coul you give some idea to resolve my problem? :-) Thanxsss!