Passing Values To Web Form

I am trying to pass a parameter from my querystring into my .aspx page, but nothing works!!  This is the string I am using to pass:
"http://www.yourwebsitehere/Test/abcd.aspx?employeename=TestName"
And I want to set the value of employeename with the value that is being passed in, this is the html for the textbox
<tr> <td nowrap="nowrap" width="108"><label for="employeename">Employee Name</label></td> <td><input name="employeename" size="40" id="employeename" type="text" runat="server"></td> </tr> And this is what I have tried to actually have the value passed displayed, but nothing is actually displaying the value...what do I need to do to have this work properly?
var script = "document.getElementById('employeename').value ...