My asp.net validation not work when i use java script

hi

i m use this function on my asp.net page


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


function prepareInputsForHints() {
    var inputs = document.getElementsByTagName("input");
    for (var i=0; i        // test to see if the hint span exists first
        if (inputs[i].parentNode.getElementsByTagName("span")[0]) {
            // the span exists!  on focus, show the hint
            inputs[i].onfocus = function () {
                this.parentNode.getElementsByTagName("span")[0].style.display = "inline";
            }
            // when the cursor moves away from the field, hide the hint
            inputs[i].onblur = function () {
                this.parentNode.getElementsByTagName("span")[0].style.display = "none";
            }
        }
    }
    // repeat the same tests as above for selects
    var selects = document.getElementsByTagName("select");
    for (var k=0; k        if (selects[k].parentNode.getElementsByTagName("span")[0]) {
            selects[k].onfocus = function () {
                this.parentNode.getElementsByTagName("span")[0].style.display = "inline";
            }
            selects[k].onblur = function () {
                this.parentNode.getElementsByTagName("span")[0].style.display = "none";
            }
        }
    }
}

this is function to show the tool tips on textbox
ok
now problem is

and i m using requierd field validation in textbox the tooltips is work but validation not work

when i remove java script function the work fine

please hel me