Ajax = function(){

		var HTTP = null;

		//cria o objeto xmlHTTP
		this.initHTTP = function(){
			try{ // Firefox, Opera 8.0+, Safari
				HTTP = new XMLHttpRequest();
			}catch(e){// Internet Explorer
				try{
					HTTP = new ActiveXObject("Msxml2.XMLHTTP");
				}catch (e){
					try{
						HTTP = new ActiveXObject("Microsoft.XMLHTTP");
					}catch (e){
						HTTP = null;
						return false;
					}//end try
				}//end try
			}//end try
			return true;
		}


		//define a função a ser chamada e que receberá a string retornada pelo HTTP
		this.configAction = function( function_name ){
			if( HTTP != null ){
				HTTP.onreadystatechange = function(){
					if (HTTP.readyState == 4){
						if(HTTP.status == 200) {
							try{
								eval( function_name+"(HTTP.responseText);");
							}catch(e){
								//alert(e.description);
							}//end try
						} else {
							alert(HTTP.statusText);
						}
					}
				}
			}
		}


		//executa a chamada a pagina e retorna o conteudo chamando a função
		this.callURL = function(URL, function_name){
			this.initHTTP();
			if( HTTP != null ){
				this.configAction(function_name);
				var d = new Date();
				var newURL = URL+"&rand="+d.getTime(); //falha caso nao haja ?
				HTTP.open("GET",newURL,true);
				HTTP.send(null);
			}else{
				alert("browser não compativel com ajax");
			}
		}
		
		
		//executa a chamada a pagina e retorna o conteudo chamando a função
		this.postURL = function(URL, dados, function_name){
			this.initHTTP();
			if( HTTP != null ){
				this.configAction(function_name);
				var d = new Date();
				var newURL = URL+"&rand="+d.getTime(); //falha caso nao haja ?
				HTTP.open("POST",newURL,true);
				HTTP.send(dados);
			}else{
				alert("browser não compativel com ajax");
			}
		}


	}