Try like the below code snippet for javascript implementation
window.onload(function(){
var cntrl= document.getElementById('<%= YourControlID.ClientID %>');
cntrl.style.display = 'none';
});
or
document.onload(function(){
var cntrl= document.getElementById('<%= YourControlID.ClientID %>');
cntrl.style.display = 'none';
});
Hope this helps.