function checkfield(loginform)
{
	
	 if(loginform.inv.value=="")
	{
		alert("Please Enter invoice no.")
		loginform.inv.focus()
		return false
	}
	else if(loginform.pass.value=="")
	{
		alert("Please enter your password.")
		loginform.pass.focus()
		return false
	}
	else if((loginform.email.value.indexOf('@') == -1) || (loginform.email.value.indexOf('.') == -1))
	{
	 alert("please enter valid email address")
	 loginform.email.value='';
	 loginform.email.focus();
	 return false
	}
                return true
     
}