function getHTTPObject() {
  try{
    http_request = new XMLHttpRequest();// Mozilla, Safari, Firefox, etc...
    try {
        if (http_request.overrideMimeType) {
            //Se possivel, ignora cabecalho usado pelo servidor e forca o padrao "text/xml". Alguns navegadores exigem esse padrao e pode dar erro se o servidor nao utilizar ele
            http_request.overrideMimeType('text/html; charset=iso-8859-1');
        }
    } catch (e1) { }
}catch(e2){
    try{
        http_request = new ActiveXObject("Msxml2.XMLHTTP");// Internet Explorer
    }catch(e3){
        try{
            http_request = new ActiveXObject("Microsoft.XMLHTTP");// Internet Explorer
        }catch(e4){
            //tratamento para alguma outra forma de implementar XMLHTTP
            http_request = false;
        }
    }
}
	return http_request;
}
var http = getHTTPObject();

function resposta()
{
	if (http.readyState == 4)
	{
		results = http.responseText;
		
		if(results.indexOf("-newsok-")==0)
		{
			/*document.getElementById("email").value="e-mail";	
			alert("E-mail cadastrado com sucesso!");*/
			alert("E-mail cadastrado com sucesso!");
			document.getElementById("news_nome").value="";
			document.getElementById("news_email").value="";
			//new Lightbox.base('box1');
		}
		else if(results.indexOf("-newsjatem-")==0)
		{
			//document.getElementById("email").value="e-mail";
			//alert("O e-mail já se encontra cadastrado em nossa base!");
			alert("O e-mail já se encontra cadastrado em nossa base!");		
			//new Lightbox.base('box1');
		}
		else
			alert(results);
	}
}

function valida_news()
{	
	erro=0;
	if(document.getElementById("news_nome").value=="")
	{
		erro=1;
		alert('Preencha o nome!');		
	}
	else if(document.getElementById("news_email").value=="" || document.getElementById("news_email").value=="e-mail")
	{
		/*document.getElementById("email_news").innerHTML = "";
		document.getElementById("email_news").style.display="";	
		document.getElementById("email_news").innerHTML = "Preencha o e-mail!";		*/
		erro=1;
		alert('Preencha o e-mail!');		
	}	
	else
	{
		emai = /^[A-Za-z0-9_.-]+@[A-Za-z0-9_.-]+.[A-Za-z0-9_.-][A-Za-z0-9_.-][A-Za-z0-9_.-]?$/;
		mail = (IsValid(document.getElementById("news_email").value,emai,1));	
		if(! mail)
		{
			/*document.getElementById("email_news").innerHTML = "";
			document.getElementById("email_news").style.display="";
			document.getElementById("email_news").innerHTML = "Formato de e-mail inválido!";*/
			erro=1;
			alert("Formato de e-mail inválido!");
		}
	}
	
	if(erro==0)
	{
		//document.getElementById("email_news").style.display="none";
		http.open("GET", "action.php?action=grava_news&email="+document.getElementById("news_email").value+"&nome="+document.getElementById("news_nome").value, true);
		http.onreadystatechange = resposta;
		http.send(null);
	}
}

<!--
    var version12 = 0;

// -->
<!--
	version12 = 1;
// -->
function IsValid(valor,reg,ema)
{
	if (ema == 1)
	{
		if(valor.indexOf("@") == -1)            // Gotta have the @ sign somewhere
			return(false);
	}
	if(valor.indexOf(" ") != -1)                 // Cant have any spaces in the address
		return(false);

	if(version12 == 1)                           // Only JS 1.2+ browsers know the RegExp object
	{
		var expre = reg;
		
		var match_result = expre.exec(valor);
		
		if(match_result == null)
		   return(false);
	}
	return(true);
}