I noticed this bug when tracking a package at the above address.
1. goto http://www.upsmailinnovations.com/tools.html
2. track a package. here I will provide my own tracking number, without concerns for privacy. Enter 9102185420705103706968
3. Mouse over the RPF link, and the pop-up will appear. It will stay and track with the mouse.
4. Move the mouse to the rightmost side of the window. The "Regional Processing Facility" popup will try to resize itself, and will come to a point when it can be sized down no longer. A horizontal scroll bar will appear, since part of the RPF popup will be obscured.
5. I am using the two-finger scrolling on my Macbook, but I am sure you can shift-scroll with a scroll wheel as well to scroll horizontally. It looks like you can scroll horizontally forever.
I'm getting the same "infinite scrolling" behavior in Firefox (although there the pop-up turns invisible).
It seems that the tracking number is no longer in the UPS database.