<ul id="tabnav">
<li id="tab_a" class="tab1"><a href="tab1.htm">Tab a</a></li>
<li id="tab_b" class="tab2"><a href="tab2.htm">Tab b</a></li>
<li id="tab_c" class="tab3"><a href="tab3.htm">Tab c</a></li>
</ul>
document.getElementById("tab_c").childNodes[0].onclick = function() {return false;};
use this concept. I hope working fine!!!!!!!!!!!!