Last year I was playing around with facebook themes/skins. I put a theme or skin (not sure if there's a difference!) on my facebook page, didn't like it, and deleted it.
On my laptop, my fb page doesn't have a theme. I don't have any add-ons or extensions that would affect fb appearance (I use Firefox). I have logged on a different fb account on my laptop and looked at my fb page, and there is no theme. I have tried a different browser on my laptop and my fb page doesn't have a theme. All well and good... BUT a friend just told me my page DOES have the theme.
So I asked my fb friends - and they are saying that the theme IS there.
How the heck do I get rid of it? I have checked add-ons and extensions, it's not there. I have checked my programs, I don't have anything that would affect themes (like GreaseMonkey). I don't have any fb apps for themes.
Where else do I look? 
And how do I know if the invisible-to-me theme is gone, if I can't see it anyway?