javascript not working with php

Hi, In a form i have two elements: I <input type="text" name="name" size=25 value="test"> II <select name="categories[]" multiple size=10> <? option value = ...?>.... <? option value = ....?>.... Now i want to show an alert message(using javascript) if the text field is empty or no option is selected from categories list. For the text field its working fine as below (the javascript method called when onsubmit method is called): if(theForm.name.value==""){ alert("You must enter a Title."); theForm.name.focus(); return(false); } But for the options list(categories) i have tried my best but i couldnt get it work. Can anyone please tell me how i can do it. Thanks anil