window.onload = function()
{
    var putHere = document.getElementById("mailing_autoiscrizione");
    createForm(putHere);
}
<!-- user = mailing_outis; query = SELECT param_value_text FROM configuration WHERE param_name='PRIVACY_TEXT' -->
function createForm(container)
{
    var form = document.createElement("form");
    form.action = "http://www.newsletterlab.com/outis/mailing/salva_autoiscrizione.php";
    form.method = "post";
    form.onsubmit = checkout;
    form.id = container.id;
    form.className = container.id;

<!-- user = mailing_outis; query = SHOW COLUMNS FROM metadata LIKE 'isSubscribe' -->
<!-- user = mailing_outis; query = SELECT * FROM metadata WHERE tableName='contacts' AND isSubscribe='Y' ORDER BY ordine -->
		var blockElement = document.createElement("p");
    	var formElement = document.createElement("label");
		var formElementInput = document.createElement("input");
		formElementInput.name = "nome";
		formElementInput.type = "text";
		if(queryString("nome") != 'false')
			formElementInput.value = queryString("nome");
		formElementInput.id = "nome";
		formElement.appendChild(document.createTextNode("nome:"));
		blockElement.appendChild(formElement);
		blockElement.appendChild(formElementInput);
				
		form.appendChild(blockElement);
				var blockElement = document.createElement("p");
    	var formElement = document.createElement("label");
		var formElementInput = document.createElement("input");
		formElementInput.name = "cognome";
		formElementInput.type = "text";
		if(queryString("cognome") != 'false')
			formElementInput.value = queryString("cognome");
		formElementInput.id = "cognome";
		formElement.appendChild(document.createTextNode("Cognome:"));
		blockElement.appendChild(formElement);
		blockElement.appendChild(formElementInput);
				
		form.appendChild(blockElement);
				var blockElement = document.createElement("p");
    	var formElement = document.createElement("label");
		var formElementInput = document.createElement("input");
		formElementInput.name = "cellulare";
		formElementInput.type = "text";
		if(queryString("cellulare") != 'false')
			formElementInput.value = queryString("cellulare");
		formElementInput.id = "cellulare";
		formElement.appendChild(document.createTextNode("Cellulare:"));
		blockElement.appendChild(formElement);
		blockElement.appendChild(formElementInput);
				
		form.appendChild(blockElement);
				var blockElement = document.createElement("p");
    	var formElement = document.createElement("label");
		formElement.appendChild(document.createTextNode("Gruppi:"));
		blockElement.appendChild(formElement);
		var divElement = document.createElement("div");
		divElement.className = "groups_row";
		<!-- user = mailing_outis; query = SHOW columns FROM groups like 'isSubscribe' -->
<!-- user = mailing_outis; query = SELECT * FROM groups WHERE isSubscribe='Y' -->
		var nobrElement = document.createElement("nobr");
		var formElementInput = document.createElement("input");
		formElementInput.type = "checkbox";
		formElementInput.value= "Teatri";
		formElementInput.name = "groups[]";
		formElementInput.id = "groups";
		nobrElement.appendChild(formElementInput);
		nobrElement.appendChild(document.createTextNode("Teatri "));
		divElement.appendChild(nobrElement);
		divElement.appendChild(document.createTextNode(" "));
		if(queryString("groups") != 'false'){
			if(queryString("groups").indexOf("Teatri") != -1)			
				formElementInput.setAttribute("checked","checked"); 
		}		
				var nobrElement = document.createElement("nobr");
		var formElementInput = document.createElement("input");
		formElementInput.type = "checkbox";
		formElementInput.value= "Eventi";
		formElementInput.name = "groups[]";
		formElementInput.id = "groups";
		nobrElement.appendChild(formElementInput);
		nobrElement.appendChild(document.createTextNode("Eventi "));
		divElement.appendChild(nobrElement);
		divElement.appendChild(document.createTextNode(" "));
		if(queryString("groups") != 'false'){
			if(queryString("groups").indexOf("Eventi") != -1)			
				formElementInput.setAttribute("checked","checked"); 
		}		
						
		blockElement.appendChild(divElement);	
		form.appendChild(blockElement);
		 
	 
	var blockElement = document.createElement("div");
	blockElement.className = "privacy_row";
	blockElement.appendChild(document.createTextNode("Ai sensi dell'articolo 13 del Codice in materia di protezione dei dati personali (D.Lgs 196/03) Le forniamo, qui di seguito, l'informativa riguardante il trattamento dei Suoi dati personali che sarà effettuato da \"Outis\" per l'erogazione dei servizi richiesti."));
	form.appendChild(blockElement);
	      
	var formElementInput = document.createElement("input");
	formElementInput.type = "checkbox";
	formElementInput.value="Y";
	formElementInput.name="privacy";
	formElementInput.id="privacy";
	form.appendChild(formElementInput);
	form.appendChild(document.createTextNode("Dichiaro di aver letto ed accettato l'informativa sulla privacy"));

	var blockElement = document.createElement("div");
    blockElement.className = "submit_row";
    var submit = document.createElement("input");
    submit.type = "submit";
    submit.value = "Invia";
    blockElement.appendChild(submit);
    form.appendChild(blockElement);
    container.appendChild(form);
    
    if(queryString("error") == 1){
    	alert('E-Mail è già registrata');
    }
    if(queryString("error") == 2){
    	alert('Non è stato compilato email');
    }    
    if(queryString("error") == 3){
    	alert('Non sono compilati tutti i campi obbligatori');
    }    
}

function checkout()
{
	if(document.getElementById("privacy").checked != true) {
		alert("Conferma di essere a conoscenza del Regolamento sulla privacy.");
	return false;
    }
    return true;
}


function PageQuery(q) {
if(q.length > 1) this.q = q.substring(1, q.length);
else this.q = null;
this.keyValuePairs = new Array();
if(q) {
for(var i=0; i < this.q.split("&").length; i++) {
this.keyValuePairs[i] = this.q.split("&")[i];
}
}
this.getKeyValuePairs = function() { return this.keyValuePairs; }
this.getValue = function(s) {
for(var j=0; j < this.keyValuePairs.length; j++) {
if(this.keyValuePairs[j].split("=")[0] == s)
return this.keyValuePairs[j].split("=")[1].replace('+', ' ');
}
return false;
}
this.getParameters = function() {
var a = new Array(this.getLength());
for(var j=0; j < this.keyValuePairs.length; j++) {
a[j] = this.keyValuePairs[j].split("=")[0];
}
return a;
}
this.getLength = function() { return this.keyValuePairs.length; } 
}
function queryString(key){
var page = new PageQuery(window.location.search); 
return unescape(page.getValue(key)); 
}