I have updated the fiddle here Fiddle should work perfect.
<script> $('#a').click(function(){
$( '.hilite' ).removeClass('hilite');
$( '#div_a' ).toggleClass('hilite');
});</script>
<script> $('#b').click(function(){
$( '.hilite' ).removeClass('hilite');
$( '#div_b' ).toggleClass('hilite');
});</script>
I have also just added id's to your div's (see fiddle).