With so many useful and exciting Add-ons within firefox its hard to pick out the best ones. My favourite is probably no script, or customize google. What is yours ?
My top one for Firefox 2 is the one that makes it look somewhat like Safari. My favorite one for Firefox 3 is the black one with blue buttons. I forgot the name of it, but it starts with an "A" Maybe you know what I'm talking about!
Seriously, this addon is awesome.
Basically, a group of university students worked out that, the new security warnings, about self-signed SSL certificates, were a problem. Great in theory, but to the average home user, a problem. What if they want to access a proxy, or another website, who doesn't have the cash to pay for a signed SSL certificate?
Perspectives however, analyzes the certificate by probing the network, and preventing attacks, such as 'man-in-the-middle'.
If Perspectives probes, and believes the page is safely self-signed, it will override the warning, and forward you onto the page. If not, you have to manually add it as an exception.