Our internet provider, which is where I also have our main email address, upgraded their web mail by adding a lot of nice features (long overdue) but also put in a rather large frame on the right side of the screen with everchanging ads. Many of them also have flickering images.
Can you say annoying?
There is a way to expand the email message to hide the ads, but each time I move to a new message, the message box shrinks to reveal the ads again.
Then I found this: Adblock Plus.
And it even has a one and a half minute video to show how it works:
It was easy to install, and now the pain is gone.