function isMail(mail){
	if (mail==""){
		return false;
	}else{
		var arroba = mail.indexOf("@");
		if ( arroba == -1 ) return false;
		if ( arroba < 2 ) return false;
		if ( mail.indexOf(".") < 2 ) return false;
		if ( mail.indexOf(".") == mail.length-1 ) return false;		
		if ( mail.indexOf("@",arroba +1) != -1 ) return false;
		if ( mail.indexOf(".@") > 0 ) return false;
		if ( mail.indexOf("@.") > 0 ) return false;
		if ( mail.indexOf(" ") != -1 ) return false;
	}
	return true;
}
function isUrl(s) {
	var regexp = /(ftp|http|https):\/\/(\w+:{0,1}\w*@)?(\S+)(:[0-9]+)?(\/|\/([\w#!:.?+=&%@!\-\/]))?/
	return regexp.test(s);
}

window.onload = function(){
	document.getElementById("form-cadastro").onsubmit = function(){
		if(document.getElementById('nome').value == ''){
			alert('Digite seu nome');
			document.getElementById('nome').focus();
			return false;
		}
		if(document.getElementById('email').value == ''){
			alert('Digite seu e-mail.');
			document.getElementById('email').focus();
			return false;
		}	
		if(!isMail(document.getElementById('email').value)){
			alert('Digite seu e-mail corretamente.');
			document.getElementById('email').focus();
			return false;
		}		
		if(document.getElementById('url').value!=''){
			if(!isUrl(document.getElementById('url').value)){
				alert('URL inválida.\nPreencha a URL corretamente ou deixe o campo em branco.');
				document.getElementById('url').focus();
				return false;			
			}
		}
	}
}