How to add self-signed certificates to different browsers?

While using Mozilla Firefox, I felt the need to add a functionality in my browser, but while I checked out the settings, I found three options, add-ons, plugins and extensions. What is the basic difference between all of them. If I want to view the page...

Last month I bought a TV at best buy. In total, I got 749 points since you get 1 point for every dollar you spend. You need 250 points for a $5 certificate. Now, I printed two certificates which totaled to be 500 points but I still had 249 left over...

I want to have more than 9 recent browsers web site in my toolbar , don't know how I can do this? where I can add some web sites?

how can i add surname on all certificates??/

I created a new website and need help putting it on all browsers besides google . My website is already on google. Please i need help!!!!!!!

I was creating a search function on a website where I added a custom button. The "button" was a input[type="reset"] that had a custom size and background image. In firefox it looked fine But in chrome a clear button was added. And...

I want to develop addon for these browsers (not necessarily for all) in Python only. I know Javascript and PHP but I dont want to use these at all (for some reasons) just pure python and it's Third party libraries. Any source or sample codes?

https://www.sciencedaily.com/ ^e.g. why is this deemed as a security threat? Jim Lai says that it could be due to ScienceDaily using a self-signed certificate.