Note: Javascript contain only disable property, no enable property. To enable or disable controls in javascript use disabled=true or disabled=false

Note: CheckBox checked event if condition use 1 or 0 don’t use true or false

<script type=”text/javascript”>

// Let’s use a lowercase function name to keep with JavaScript conventions

function chkChecked(invoker) {

// alert(”Checked”);

// document.getElementById(’<%=butSubmit.ClientID%>’).disabled=false;

//javascript checkbox value

var myElement = document.getElementById(’<%=chk.ClientID%>’);

//1 means true     0 means false

if(myElement.checked == 1)

{

//javascript enable button

document.getElementById(’<%=butSubmit.ClientID%>’).disabled=false;

}

else

{

//javascript disable button

document.getElementById(’<%=butSubmit.ClientID%>’).disabled=true;

}

}

</script>

First Method: <asp:CheckBox ID=”chk” runat=”server” Text=”I Agree” onClick=”return chkChecked(this)”/>

Second Method: chk.Attributes.Add(”onClick”, “chkChecked(this)”);