How to disable li object in mozilla : I am new to JS and trying to modify code to make it browser compatible. Using below code I am trying to create tabs (link) and by default menu_item3 & 4 will be disable. This code is not working on mozilla & chrome whereas working in IE.
<ul>
   <li id="menu_item1" class="selectedtab"><a href="javascript:;" onclick="showTab(this)"><span style="color:black; font-weight: bold;">Report Options</span>
</a></li>
                <li id="menu_item2"><a href="javascript:;" onclick="showTab(this)"><span style="color:black; font-weight: bold;">Required Filters</span></a></li>
                <li id="menu_item3" class="disabled-state"><a href="javascript:;" onclick="showTab(this)" disabled='disabled'><span style="color:black; font-weight: bold;">Optional Filters</span></a></li>
                 <li id="menu_item4" class="disabled-state"><a href="javascript:;" onclick="showTab(this)" disabled='disabled'><span style="color:black; font-weight: bold;">Confirmation</span></a></li>

Thanks,
AS
 </ul>