Accessing Server Controls Using JavaScript

Suppose you have a Web server control called TextBox in your Web page:

<asp:TextBox id="Test" Text="Sample" runat="server">

You can access this value in a couple ways using JavaScript:

1. 
   document.getElementById('<%=Test.ClientID%>').value;
   
   ClientID - server control identifier generated by ASP.NET
   

2. 
   document.forms[0]['Test'].value;

   Note: Copy - Paste from this site http://www.devx.com/tips/Tip/28332