What's interesting is that your preview picture matches what I see in the forum, but not your forum picture...
I just checked to make sure I didn't mislabel the file attachments, but they seem to be right. (In fact, in the "preview" attachment, you can see where it says "preview" at the top, in the blue rectangle.)
What Browser are you using?
The text size seems extra big - have you increased your font size settings?
Nope. Text rendering set to 100%. And page-rendering mode is set to "Author Mode", so it should be rendering in conformance with your CSS.