Copying / pasting element from Ffox/ Chrome

There will always be discrepancies because the actual conversion is very complex, even though it doesn't look like it is. We are talking about different languages (word processor applications and internet pages), that run on various browsers (IE, Firefox, Chrome, Opera, etc.). Each browser handles pasting differently. CKEditor is actually well-known for its conversion faithfulness. What you have to understand is that even though the formatting might not look exactly the same, it maintains much the important syntax. So text formatted to Heading 1 in Word or <h1> in another browser won't simply convert to a large font with bold when pasted to CKEditor; it will be converted to a header with an <h1> tag - something that is very useful online. But ya, discrepancies will crop up because we're dealing with many unseen things.

Each browser has different policies with regards to how they copy and paste from the clipboard, so using two different browsers maximizes the risk of having problems and CKEditor can't fix that because the data that it gets is simply missing some part of the information.

Besides that, certain browser versions might have new bugs like happened with recent versions of Firefox that had problems pasting from word and they might also be related to your problem. In that case you should find out which browser is to blame and make sure that it's reported at its development site so it can be fixed back.