function ajax_request(methode, url, arguments,type, fonction) {
         var http_request = false; /** http_request est la variable qui contient notre objet "ajax"*/
         var data=null; /** data est la variable qui contient les arguments*/
         var taille=0; /** taille est la variable qui la taille de data*/

         if(methode != "GET") {
                  if(methode != "POST") {
                          alert("Requete Ajax : methode incorrecte -> " + methode);
                          return false;
                  }
         }

         if(!arguments) {
                 arguments='';
         }

         if(type != "responseText") {
                 if(type != "responseXML") {
                          alert("Requete Ajax : type incorrecte -> " + type);
                          return false;
                 }
         }

         if(!url) {
                 alert("Requete Ajax : url incorrecte");
                 return false;
         }

         if(!fonction) {
                 alert("Requete Ajax : fonction incorrecte");
                 return false;
         }else{
                 fonction=fonction+"(http_request."+type+")";
         }

         if(methode == "GET") {
                 url+="?"+arguments;
         } else {
                 data=arguments;
                 taille=data.length;
         }


         if (window.XMLHttpRequest) {
             http_request = new XMLHttpRequest();
             if (http_request.overrideMimeType) {
                 http_request.overrideMimeType('text/xml');
             }
         } else {
             if (window.ActiveXObject) {
                 try {
                     http_request = new ActiveXObject("Msxml2.XMLHTTP");
                 } catch (e) {
                     try {
                          http_request = new ActiveXObject("Microsoft.XMLHTTP");
                     } catch (e) {}
                 }
             }
         }

         if (!http_request) {
              alert('Cannot create an XMLHTTP instance');
              return false;
         } else {
             http_request.onreadystatechange = function() {
                 if (http_request.readyState == 4) {
                      if (http_request.status == 200) {
                               eval(fonction);
                               return true;
                      } else {
                               alert("Error no."+http_request.status+"\nAn error occur while receiving data");
                               return false;
                      }
                 }

             }
             http_request.open(methode, url ,true);
             http_request.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
             http_request.setRequestHeader("Content-length", taille);
             http_request.setRequestHeader("Cache-Control", "no-cache");
             http_request.setRequestHeader("Connection", "close");
             http_request.send(data);
         }
}

    function principal(reponse) {
        document.getElementById("contenu").innerHTML = reponse;
    }