Somehow, it seems that Firefox handles <select multiple> in a different and unknown way from what Opera and Konqueror do, and different from the W3C standard. This simplified test page validates, and works in Opera and Konqueror (presumably IE too), but in Firefox 3.0 it doesn't pre-select the selected options and when you make a selection in one of the boxes it undoes your selection in the other box: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html><head><title>Test</title></head> <body> <form action=""> Box 1:<br> <select multiple size="5" name="parsecodelinks[]"> <option value="title">title</option> <option value="url">url</option> <option value="description" selected>description</option> <option value="email">email</option> </select> <br>Box 2:<br> <select multiple size="5" name="parsecodecategories[]"> <option value="name">name</option> <option value="description" selected>description</option> <option value="custom">custom</option> <option value="moderators">moderators</option> </select> </form> </body> </html> Code (markup): Any ideas? Frustrating when something ridiculously simple fails in one browser. Couldn't find anything relevant in google.