Undefined?

Can someone tell me why I keep getting this on the farthest right hand side of my screen in my website?:

undefined

undefined

undefined

undefined

undefined

undefined

undefined

undefined

Where did you get it?

My website just started to display this too Where it comes from? It's displayed every 5-10 seconds on the upper right corner. What could be the source? I will post screenshot soon

Edit: Screenshot added. The undefined messages blend in and out every 10 seconds or so. Even i do not browse the website.

Edit2: I found out It's the notification window and this is being posted into it:

<div id="notification_window" class="notifi_window">
     <div class="notifi" style="display: block; ">undefined</div>
     <div class="notifi" style="display: block; ">undefined</div>
     <div class="notifi" style="display: block; ">undefined</div>
</div>

Hello

This DIV is used to display Ajax based notifications. Floating member menu checks for updates from time to time and displays popup bubbles in this DIV if something new appeared. Looks like for some reason script returns 'undefined' instead of an emty value or so.  The following URL is used to get updates.

http://www.domain.com/member_menu_queries.php?action=get_bubbles_values&bubbles=...&_r=...

Solved: I found it. It was being caused by another script i injected into _header.html and _header2.html

Thanks for your help anyway :)