You've left out some important information, like what does the pop-up say?
For example, Avast Anti-Virus shows pop-ups in the bottom RH corner every time it updates itself - this is normal behaviour and nothing to worry about.
By clicking on the User Name, you will requery the forum for that user. You will see everything that he or she has posted with that Mudcat name.
By clicking on the Thread Name, you will be sent to the Forum on that thread as if you selected it from the main Mudcat Forum page.
By clicking on the Subject, you will also go to the thread as if you selected it from the original Forum page, but also go directly to that particular message.
By clicking on the Date (Posted), you will dig out every message posted that day.
sj