First Create the Prompt in the HEAD of your document

<script language=JavaScript> <!--- start of javascript hide var UserName=prompt("Enter your Firstname :","UserName"); // unhide ---> </script>

Next, place this code where you want the variable contents to display

<script language=JavaScript> <!--- start of javascript hide document.write("<H1 ALIGN=center>Hello " + " "); document.write(UserName + " "); document.write("</H1>"); //unhide ---> </script>