This is caused by using the copying then pasting from an application such as Microsoft Word. The text you see in word also includes a great deal of formatting information that you cannot see. This is what allows you to see a file exactly as it was created on other computers.
To remove this text you can paste the information into notepad, and then paste it into the form field. At this point you can use the tools provide to edit the font color and size.
You may also use the “Source” feature to see the HTML version of your article. When you locate the offending code, you can delete it and save your work.