vikaslalkiya

<script type="text/javascript">
        {
            var hiddenControl = '<%= hdnDirtyFlag.ClientID %>';
            document.getElementById(hiddenControl).style.color = "red";

        }
                 
                        </script>

Hello,

No point of changing the color in hidden field since it will never get shown at client side. Change the above code to below and it will work for the label. Also I don't see that you've defined any function. placing the script inside curly braces alone would not work.

<script type="text/javascript">
        window.onload = function test(){
            var hiddenControl = '<%= Label1.ClientID %>';
            document.getElementById(hiddenControl).style.color = "red";
        }
</script>

Following link will help you to learn about javascripts.

http://www.w3schools.com/js/

vikaslalkiya

protected void Page_Load(object sender, EventArgs e)
    {
        hdnDirtyFlag.Value = "Label1";

    }

What are you trying to achieve?