function checkRegistration(){
	if(!document.form1.agree.checked){
		alert("You must agree to the MediaWars terms and privacy policy to register a MediaWars account.");
		return false;
	}else if(!checkAge()){
		alert("You must be 18 or older to register a MediaWars account.");
		return false;
	}else if(document.form1.gender.value.substring(0,1) == "("){
		alert("Please choose your gender from the drop down box.");
		return false;
	}else if(document.form1.nationality.value.substring(0,1) == "("){
		alert("Please choose your nationality from the drop down box.");
		return false;
	}else if(document.form1.realName.value.substring(0,1) == ""){
		alert("Please enter your real name.");
		return false;
	}else if(!validateZIP()){
		return false;
	}else{
		return true;
	}
}

<!-- Zip Check Original:  Brian Swalwell -->

<!-- This script and many more are available free online at -->
<!-- The JavaScript Source!! http://javascript.internet.com -->

<!-- Begin
function validateZIP() {
var field = (document.form1.zip.value);
var valid = "0123456789-";
var hyphencount = 0;

if (field.length!=5 && field.length!=10) {
alert("Please enter your 5 digit or 5 digit+4 zip code.");
return false;
}
for (var i=0; i < field.length; i++) {
temp = "" + field.substring(i, i+1);
if (temp == "-") hyphencount++;
if (valid.indexOf(temp) == "-1") {
alert("Invalid characters in your zip code.  Please try again.");
return false;
}
if ((hyphencount > 1) || ((field.length==10) && ""+field.charAt(5)!="-")) {
alert("The hyphen character should be used with a properly formatted 5 digit+four zip code, like '12345-6789'.   Please try again.");
return false;
   }
}
return true;
}
//  End -->

function checkAge(){
	/* the minumum age to allow in */
	var min_age = 18;

	/* change "age_form" to whatever your form has for a name="..." */
	var year = parseInt(document.form1.dobyear.value);
	var month = parseInt(document.form1.dobmonth.value) - 1;
	var day = parseInt(document.form1.dobday.value);

	var theirDate = new Date((year + min_age), month, day);
	var today = new Date;

	if ( (today.getTime() - theirDate.getTime()) < 0) {
		return false;
	}
	else {
		return true;
	}
}