function jsValidateForm()
{
    if (document.getElementById("ctl00_ContentPlaceHolder1_txtUserName").value=="")
    {
        alert("Please enter Username.");
        document.getElementById("ctl00_ContentPlaceHolder1_txtUserName").focus();
        return false;
    }
    if (document.getElementById("ctl00_ContentPlaceHolder1_txtPassword").value=="")
    {
        alert("Please enter Password.");
        document.getElementById("ctl00_ContentPlaceHolder1_txtPassword").focus();
        return false;
    }    
}