If your text was copied from a Word document or a website and then pasted into TYPO3, it might be necessary to remove any formatting. If you do not remove the formatting, the text on the website could show in a different font and size, on the frontend. It can also effect the functionality of the website.
You can remove formatting by selecting the 'Remove Format' icon (2), but It is necessary to mark the text before (1). (4.6.1)