When copying text from one application and pasting it into another one, you usually get to keep the formatting of the text as well. With formatting, I here refer to font size, text color, bold, hyperlinks, et cetera.
The program is no longer updated. Last version, released in December 2011, can be still downloaded from the official website.
With this addon you can copy selected text without any formatting such as italic, bold, font size, etc. Just select text, right click and from context menu choose "Copy as plain text".