How to show message box in Ajax.

when we use Ajax tools in our application and then we need to show pop-up on the button click. But pop-up does not occur on the page. The problem is little bit time consuming because we can't understand easily what's going on? For that use this code.Because the solution is very simple :


Button1.Attributes.Add("onclick", "javascript:return " +
"alert('All fields are mandatory. " +
"')");

//Button1 is the ID of Button.