If you don`t know how to make a custom profile, read my blog on it.

Trick one: Popup Message
Add this to the blog title:
alert("Hello there!"

In this case, the text "Hello there!" will show up inside the popup.

Raw code:
<script type=text/javascript>alert("Hello there!"</script>


Trick two: Greeting message
In this trick, you will see text show up at the top of the profile, greeting the user.
Make this the blog title:

<span style="position:absolute; left:0; top:0; color:red">Hi! Welcome!</span>

In this case, "Hi! Welcome!" will show up at the top of the page in red font.

Raw code:
<span style="position:absolute; left:0; top:0; color:red">Hi! Welcome!</span>


If you know a trick, post it in the comments!