function chk_form ( ){
		if(document.getElementById('first_name').value == '') {
			alert('Please enter your first name.');
			document.getElementById('first_name').focus();
			return false;
		}
		if(document.getElementById('last_name').value == '') {
			alert('Please enter your last name.');
			document.getElementById('last_name').focus();
			return false;
		}
		if(document.getElementById('company').value == '') {
			alert('Please enter your company name.');
			document.getElementById('company').focus();
			return false;
		}
		if(document.getElementById('email').value == '') {
			alert('Please enter your email address.');
			document.getElementById('email').focus();
			return false;
		}
		if(document.getElementById('phone').value == '') {
			alert('Please enter your phone number.');
			document.getElementById('phone').focus();
			return false;
		}
		else {
			var reg = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;
			var address = document.getElementById('email').value;
			if(reg.test(address) == false) {
				alert('Please enter a valid email address.');
				document.getElementById('email').focus();
				return false;
			}
		}
	}