For example : Suppose i want to add two number and show the result. I want to perform addition in client side and show the result on content page's Label control.
for this first i wrote the below code :
document.getElementById('Label1').innerHTML = result;
Because the content page's control id converted as per contentplace holder id.
So i modified the code to below code.
document.getElementById('<%=Label1.ClientID%>').innerHTML = result;
The above code works fine.
so whenever you want to access the content page's control at client side just put the clientID of that control not the control id only.