Use the Up and Down arrows while in the textbox to cycle through your choices. InternetExplorer users can go up and down through the list, Netscape users can only go down through the list. Neat!
The idea of this JavaScript is very simple. Just define one layer for every size you need. In academical therms it is not correct; but in the reality, we can supose that the maximum size that a list will have could be about 10 (and <50 physically).
When selecting a value from the first combo box, thesecond combo box will be filled in with new valuescorresponding to the selection from the first combo box.