I recently read an article about Firefox tweaks that would speed up page loading time by changing several settings in the about:config dialog. I knew those tweaks but decided to take a look if my settings were different from the ones mentioned in the article.
I found out - to my big surprise - that I was running Firefox with the default settings and not the tweaked settings. I had the feeling that Firefox was running slower than before after the latest update but I was not able to determine the cause, until now that is.