whats wrong ?
Check your zoom and make sure it's on 100%
Do you think that you could give me a screenshot of your html? I can't see anything wrong with your css as of now, and it looks like you are zoomed at 100%. But I would suggest writing it as 50.2px right now to bypass the error.
I personally like to make a space. For example, instead of "height:50px;" I would write "height:_50px;" (of course without the _). Try that, see if it works