If you have multiple tabs going, and are typing in a text area or textfield
in one while another tab or window is in the process of loading, when it
completes loading you will loose focus (and selection of you have it) of
text in what you are typing in.  The user must click in the textfield or
textarea to restore the ability to type.

This is very annoying, especially if you are needing to surf at the same
time as typing in any data to a web browser.

To duplicate:
1 - open a browser to any page that has a textarea (such as this one). 
2 - click in the text area and type something.
3 - open another tab and load a slow website (such as something like
http://everything2.com/index.pl?node=galeon)
4 - quickly switch back to the original window and type.  

You'll notice that when the other tab turns blue (if you use that setting)
from red to indicate it has finished loading that you can no longer type.