Usually slowness after one upgrade requires disabling hardware acceleration, or a possible new regression (hopefully not).

You might need to restart Firefox in order for this to take effect, so save all work first (e.g., mail you are composing, online documents you're editing, etc.).

Then perform these steps:

• Click the orange Firefox button at the top left, then select the "Options" button, or, if there is no Firefox button at the top, go to Tools > Options.
• In the Firefox options window click the Advanced tab, then select "General".
• In the settings list, you should find the Use hardware acceleration when available checkbox. Uncheck this checkbox.
• Now, restart Firefox and see if the problems persist.

Additionally, please check for updates for your graphics driver by following the steps mentioned in the following Knowledge base articles:

Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

Upgrade your graphics drivers to use hardware acceleration and WebGL

Hi Aman,

Thank you for your reply. I had hardware acceleration off from a previous "why does this lag" period so that was not the problem.

I did manage to solve this, however, unfortunately the solution is one of two:

1. I downgraded back to version 26, which was the last one that worked properly for me
2. I disabled Skype Click and Call or whatever it's called.

Now I'm back to smooth scolling and browsing. I personally believe it was Skype's fault, the only way I can check this is to upgrade back to 27 again and see if the problem reappears.

Skype has long been known for its problematic addon. It tends to cause lag when loading pages and with websites that modify the page frequently (as in the case of YouTube and Gmail).

I personally recommend keeping Skype's addon disabled and upgrading to Firefox 27 again.

Good luck!