Dlzka premennej

premenna = premenna.substr(0, 512)

AJAX.open("POST", url, true);
AJAX.send(null);

function postText() {
   var AJAX = null;
   if (window.XMLHttpRequest) {
      AJAX=new XMLHttpRequest();
   } else {
      AJAX=new ActiveXObject("Microsoft.XMLHTTP");
   }
   if (AJAX==null) {
      alert("Your browser doesn't support AJAX.");
      return false
   }
   AJAX.onreadystatechange = function() {
      if (AJAX.readyState==4 || AJAX.readyState=="complete") {
         callback(AJAX.responseText, AJAX.status);
      }
   }
   var vyber = document.getElementById(main).innerHTML;
   var url='index.php?text='+encodeURIComponent(vyber);
   AJAX.open("POST", url, true);
   AJAX.send(null);
   
}

window.onload = postText;

function postText()
{
   var AJAX = null;
   if (window.XMLHttpRequest) {
      AJAX=new XMLHttpRequest();
   } else {
      AJAX=new ActiveXObject("Microsoft.XMLHTTP");
   }
   if (AJAX==null) {
      alert("Your browser doesn't support AJAX.");
      return false
   }
   AJAX.onreadystatechange = function() {
      if (AJAX.readyState==4 || AJAX.readyState=="complete") {
         callback(AJAX.responseText, AJAX.status);
      }
   }
   var vyber = document.getElementById(main).innerHTML;
   var url='index.php';
   AJAX.open("POST", url, true);
   AJAX.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
   if (AJAX.overrideMimeType)
   {
      AJAX.setRequestHeader('Connection', 'close');
   }
   AJAX.send('text='+encodeURIComponent(vyber));
   
}

window.onload = postText;