Putting focus on a field in a webusercontrol

I have a textbox on a webusercontrol thats on a webusercontrol thats on a webusercontrol thats on a page.
I tried using the javascript below but it cant find the control. Can anyone help me ?
 
<asp:Content ID="Content1" ContentPlaceHolderID="CustomerContentPlaceHolder" Runat="Server">
<SCRIPT language=javascript>
    var control = document.getElementById("ctl00$CustomerContentPlaceHolder$NewLeadTabsWebUserControl1$TabContainer1$TabPanel1$LeadSummaryDetailsWebUserControl1$LeadNameAndPhoneNumberWebUserControl1$FirstNameTextBox");
    alert(control)
    if( control != null ){control.focus();}
</SCRIPT>

 
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