function SubmitForm() {
	// variable to hold the error message
	var strErrorMessage = "";
	// variable to hold regular expression for email validation
	var filter  = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
	// check for errors and set the error message
	if (trim(document.getElementById("CompanyName").value) == "") {
		strErrorMessage += "Please enter your company name.\n";
		changeColour("CompanyName", true);
	} else changeColour("CompanyName", false);
	if (trim(document.getElementById("name").value) == "") {
		strErrorMessage += "Please enter your name.\n";
		changeColour("name", true);
	} else changeColour("name", false);
	if (trim(document.getElementById("PhoneNumber").value) == "" || trim(document.getElementById("email_from").value) == "") {
		strErrorMessage += "Please enter your phone number and email address.\n";
		changeColour("PhoneNumber", true);
		changeColour("PhoneAreaCode", true);
		changeColour("email_from", true);
	} else {
		changeColour("PhoneNumber", false);
		changeColour("PhoneAreaCode", false);
		changeColour("email_from", false);
	}
	if (trim(document.getElementById("email_from").value) != "" && !filter.test(trim(document.getElementById("email_from").value))) {
		strErrorMessage += "Your email address appears to be invalid.\n";
		changeColour("email_from", true);
	} else if (trim(document.getElementById("email_from").value) != "") changeColour("email_from", false);
	if (trim(document.getElementById("Message").value) == "") {
		strErrorMessage += "Please enter your message.\n";
		changeColour("Message", true);
	} else changeColour("Message", false);
	// check if there are errors and output error message or submit the form
	if (String(strErrorMessage) != "") alert("You must fix the following errors before submitting the form:\n\n" + strErrorMessage);
	else document.forms[0].submit();
	
	return false;
}
function changeColour(el, blColour) {
	document.getElementById(el).style.backgroundColor = blColour ? "#FFCECE" : "";
}
function trim(str) {
	return str.replace(/^\s*|\s*$/g, "");
}