function colorRows() {
       var myTR = document.getElementsByTagName('tr');
       for (var i=0;i<myTR.length;i++) {
               if (i%2) {
                       myTR[i].className = 'rowTint';
               }
       }
}

function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      if (oldonload) {
        oldonload();
      }
      func();
    }
  }
}

addLoadEvent(colorRows);
addLoadEvent(function() {
  /* more code to run on page load */ 
});