Doesn't work. I have my own HTML page of links, and after I used this, those links that have been accessed still show as having been accessed, and my browsing history still pops up from the address bar. So despite telling it to clear EVERYTHING, it clearly doesn't. Don't bother.
I set it to delete all the data, including cookies and login data such as passwords, set the time period to "everything" but I was still logged in to all the sites and Firefox still suggested form data.
I'm confused by this plugin. They show a graphic that led me to believe it's exactly what I was looking for, but when you install it, there are no options like you see in the graphic. Had it been like the graphic shows, I probably would have given it 5 stars.