You have probably changed your display properties for these forums.
If you scroll down to the very bottom left of the screen you will see two drop-down boxes. The one the right is to select your language & the one on the left selects what background you will get when you log in. Try experimenting with different ones until you find the one you like.
I prefer haylazblue, which gives me a white background with balck text. The problem is that some members use a different choice with a dark background so they can't read my posts (or, at least... that's what they claim
).
JCC