[themes] Themeing based on url alias path

I am trying to do the following but having issues. I would like to insert a specific div tag in my page.tpl.php when the url alias contains yepp for example when www.domain.com/yepp or www.domain.com/yepp/page1 If I try using arg(0) it just returns the internal system path "node". Any help would be greatly appreciated. Thank you -- Chris McCreery