The regular expression you seek is: [^"]*
so if you want to change all these:
<a class="wildcat" href="lion.html">
<a class="wildcat" href="tiger.html">
<a class="wildcat" href="leopard.html">
to:
<a class="wildcat" href="bigcat.html">
you search for:
<a class="wildcat" href="[^"]*">
and replace with:
<a class="wildcat" href="bigcat.html">
(make sure you tick the match case & regular expressions + seclect 'source code')