about java script and how to use it in web application

<input type="checkbox" id="chk1" name="chk" />

//One button to call that script function 

<asp:LinkButton ID="lnk_Register"  OnClientClick="javascript:return validate();" runat="server" </asp:LinkButton>

//finally your javascript code 

<pre lang="xml"><script type="text/javascript">
        function validate() {

            if (document.getElementById('chk1').checked == true) {
                return true;
            }
            else {
                alert("You Must Agree To Terms");
                return false;
            }
        }
    </script>