change of theme

[Jashmi]

My problem is that i don't know what code should i have to put in header section for change of theme ?

I'm using following code in body section

<link rel="stylesheet" type="text/css" href="styles/lib.css" /><div id="lib-bar" class="x-toolbar" style="border-width:0 1px 1px"><div id="lib-bar-inner"> <span>Theme:</span> <select id="exttheme"><option value="default">Ext Blue</option><option value="gray">Gray Theme</option><option value="green">Green Theme</option></select></div></div>