function checkform(f)
{
	if (f.ContactName.value == "")
	{
		alert("Please enter your name"); 
		f.ContactName.focus();
		return false;
	}
	
	if (f.EmailAddress.value == ""  &&  f.PhoneNumber.value == "")
	{
		alert("Please enter either a phone number or email address so that we may contact you back"); 
		f.EmailAddress.focus();
		return false;
	}
	else
	{
		if (f.EmailAddress.value != "")
		{
			if (f.EmailAddress.value.indexOf('@',0)==-1  ||  f.EmailAddress.value.indexOf('.',0)==-1)
			{
				alert(f.EmailAddress.value + " is not a valid email address");
				f.EmailAddress.focus();
				return false;
			}
		}
	}
	
	if (f.Enquiry.value == "")
	{
		alert("You must enter an enquiry");
		f.Enquiry.focus();
		return false;
	}
	
	alert("Thank you for your enquiry");
}