(Before beginning this phase of the test, I will start Firefox for the tester. Note that on Fedora Linux, Firefox starts up with a default home page from the Fedora project.)
1. You would like to see what's happening in the news. Your favorite news website is BBC News, but you don't remember the website's address.
Search for the BBC News website, and bring up the site.
2. You would like to bring up the BBC News website every time you start up the web browser. Please set the BBC News website as the default page.
3. You don't have your glasses with you, so it's hard to read the text on the BBC News website. Please make the text bigger on the BBC News website.
4. You now would like to see what's new with your favorite "open source" project, FreeDOS. The website's address is http://www.freedos.org/
However, you want to keep an eye on the news while you are looking at the FreeDOS website. In a new site, navigate to the FreeDOS website.
5. You would like to save a copy of the FreeDOS front page, so you can view it later on your laptop during your bus ride home tonight. Save a copy of the page to the Documents folder.
6. You decide to download a copy of the FreeDOS program screenshot, the sample program image on the right side, under "Welcome to FreeDOS". This image might come in handy for a document you are working on (writing the document is not part of this exercise).
Save a copy of this image as freedos.png in the Pictures folder.
7. You would like to visit the FreeDOS website later, but don't want to keep typing in the address every time. Create a bookmark for the FreeDOS website.
When you create the bookmark, name it simply FreeDOS.
(UPDATE 11/8/12) After some discussion, I've decided to drop scenario 8 from the usability test. Installing Adblock Plus is not a task that "typical" users with "average" knowledge would be expected to do.
* See, this is one of those times that user personas and usage scenarios would come in handy! We would be able to refer back to those to decide if Firefox's "typical" users would need to install add-ons like Adblock Plus.