function check_form(f) {	
	if(document.getElementById("name")){
		if(f.name.value.length < 1 ){
			alert('Please inform your name');
			f.name.focus();
			return false;	
		}		
	}
	if(document.getElementById("email")){		
		if(f.email.value.length < 1 ){
			alert('Please inform your e-mail');
			f.email.focus(); // put the prompt in the name field 
			return false;
		}
		if(!check_email(f.email.value)){
			alert('Invalid e-mail');
			f.email.focus();
			return false;
		}
	}		
	if(document.getElementById("message")){
		if(f.message.value.length < 1 ) {
			alert('Please write your message');
			f.message.focus();
			return false;	
		}			
	}
	alert('Your message has been sent. Thank you!');
}

function check_email(e) {
ok = "1234567890qwertyuiop[]asdfghjklzxcvbnm.@-_QWERTYUIOPASDFGHJKLZXCVBNM";

for(i=0; i < e.length ;i++){
	if(ok.indexOf(e.charAt(i))<0){ 
	return (false);}	
	} 
	if (document.images) {
		re = /(@.*@)|(\.\.)|(^\.)|(^@)|(@$)|(\.$)|(@\.)/;
		re_two = /^.+\@(\[?)[a-zA-Z0-9\-\.]+\.([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$/;
		if (!e.match(re) && e.match(re_two)) {
			return (-1);	} 
	}
}