styling tab when clicked

Yeah, you can do it with a javascript, although I would use server-side solution.

Example:
<!-- STYLE -->
.tabs .current {
  background-color: blue;
}

<!-- Your tabs -->
<div class="tabs">
<a href="test.html">Test.html</a>
<a href="test2.html">Test2.html</a>
</div>
<script type="text/javascript">
  function highlight_tab() {
    var links = document.getElementsByTagName('a');
    for (i = 0; i < links.length; i++) {
      var href = links[i].href;
      if (window.location.href.match(href) != null) {
        links[i].className += " current";
      }
    }
  }

  window.onload = highlight_tab;
</script>

How it works:

It goes through all the links on the page. Checks their href attribute against current location and if location contains it, applies "current" class to the matching link.

That's basic version of the script, it will not work with relative urls, and probably contains some bugs that will cause hightlighting wrong <a> elements, or maybe highlighting more than one.