Javascript function for current class

I ve created a text widget with links.

I m trying to highlight the site I m currently on

(current class).

I wanted to achieve this by pasting the following code in my
header.php

but it doesnt seem to work.

any idea why ?

<script type="text/javascript">
$(function() {
     var pgurl = window.location.href.substr(window.location.href
.lastIndexOf("/")+1);
     $("#custom-side ul li a").each(function(){
          if($(this).attr("href") == pgurl)
          $(this).addClass("selected");
     })
});
</script>