Two things annoy me a lot when I'm browsing the Internet. First, I hate unclickable links, where I have to select the text link, open a new tab, paste the link, then press enter. I'd much rather deal with links that I can just click to open. The other issue is being forced to manually edit a URL in the address bar if I want to browse up one level on a site. Linkification and Uppity are two Firefox extensions that make my annoyances go away.
Installing these Firefox extensions, like installing any other Firefox extension, is just a matter of clicking the shiny green Install Now button from the extensions' homepages. You'll find both the extensions enabled after a browser restart to complete the installation.
For an example of why you might want to use the Linkification extension, visit its home page.