Originally Posted by Tom S.

I disagree. I didn't have the problem until Firefox updated itself a few months back. Literally the first time I used it after the update, I started getting double line spacing every time I hit the return key. Nor is it limited to this forum - it happens elsewhere as well. I suspect if one delves far enough into FF's settings something can be changed to effect a cure. I did do a bit of investigation but got sidetracked. The issue goes away if I fire up an old version of IE, but since that browser is no longer supported by MS, I don't feel comfortable using it much.

I would agree that the problem may not be entirely FF's fault. Perhaps it's a result of a plug in or the program's interaction with Norton or Malwarebytes. In either case though, it only happens with FF and therefore has something to do with that browser.