Just wanted to post a solution to a problem I was having that I found by reading random threads...
My phone (Android) suddenly stopped showing the mobile site and it was driving me crazy zooming in and out to read posts.
Logging in and out didnt work, I had to clear my cache.
On firefox, all I did was go to the settings, privacy data, clear history, clear now. I've attached a screen shot of the options I selected. Now it's back to the normal mobile site :)
Hope that helps some people :)