I have often seen that web pages, also sometimes the application that I am currently working on display some garbage texts in some specific areas of the page only. Also this problem is sporadic and doesn't happen always. An example of what I mean by garbage is shown in the screenshot below from yahoo mail :
What is the reason for such a behavior? obviously it can't be an encoding issue because the content of rest of the page looks okay.
The issue occurred in Firefox and went away after a full page refresh.