Every time I click a link, it opens in a new tab instead of the existing one.
Whenever I left click on any link, Firefox opens the link in a new tab. Previously it would only open a link in a new tab if I either middle clicked, or right clicked and specifically selected 'Open Link in New Tab.'
Re: Every time I click a link, it opens in a new tab instead of the existing one.
This may be because the site is instructing the browser to open them in a new tab (I know, it's a big usability issue, but the web is still young...). Can you try it on other browsers and see what happens? If the same happens, yes, it's probably the site that's telling the browser to open the link in another tab.
If you want to eliminate that behavior, and be in full control of where the links open (middle click to open in new tab, left click to open in the same tab - as it should be), I suggest you install an extension like Tab Mix Plus, which, among other things (many things, it's an absolutely phenomenal extension) will let you configure "links that open in a new window" to open on the current tab.