<select id="select1" name="select1" onchanged="getSelectValue(this);">

<input id="hidGetValue" type="hidden" runat=server/>

function getSelectValue(obj)
{
   //for(var i=0;i<this.options.length;i++)
   //{
   //}
   var hid=document.getElementById("hidGetValue");
   hid.value=this.options(this.selectedIndex).value;
}