function checknull()
{
	var minlength=6;//minimum length for password
	var maxlength=12;//maximum length for password
	if(document.form.txtFname.value=="" || document.form.email.value=="" || document.form.phone.value=="" || document.form.comments.value=="") 
	{
		alert("Mandatory fields cannot empty");
		return false;
	}
	if(isEmail(document.form.email.value) == false)
	{
		alert("Enter Valid Email address");
		document.form.email.value="";
		document.form.email.focus();
		return false;
	}
	function isEmail(string) 
	{
    if (string.search(/^\w+((-\w+)|(\.\w+))*\@[A-Za-z0-9]+((\.|-)[A-Za-z0-9]+)*\.[A-Za-z0-9]+$/) != -1)
        return true;
    else
        return false;
	}
}