add_option is defined in j1.js as this:
tstr = sel_obj.length + " th item";
new Option(tstr, tstr);
This code works fine in Internet Explorer 4 and all versions of Netscape, but I can't get it to work in IE5.
This is tough. Other than possibly deleting the space between alert and (sel_obj.name), I don't see any reason why it shouldn't work. I do know that in IE5, the object model for adding an option to a select box is syntactically a little different here than what you have:
This code definitely works. Note that the name of the element to be created must be in uppercase.