function btnConform(){
 var inputs = document.getElementsByTagName("input");
 for( var i=0,j=inputs.length; i<j; i++){
  var btn = inputs[i]; 
  if(btn.getAttribute("class") ){
   if(btn.getAttribute("class") == "input_btn"){
    btn.onmouseover = function(){
     btn.style.backgroundPosition = 'left -27px';
     return false;
    }
    btn.onmouseout = function(){
     btn.style.backgroundPosition = 'left top';
     return false;
    }
   }
  }
  else if(btn.getAttribute("className")){
   if(btn.getAttribute("className") == "input_btn"){
    btn.onmouseover = function(){
     btn.style.backgroundPosition = 'left -27px';
     return false;
    }
    btn.onmouseout = function(){
     btn.style.backgroundPosition = 'left top';
     return false;
    }
   }
  }
 }
}

window.onload = btnConform;