White fonting is an old school SEO technique where you use white text on a white background to hide keywords on a page.
Back when you could rank stuff by increasing the keyword density (number of times a term appeared on a page). It was a tactic used to manipulate search engines by getting more keywords on a page, but ‘hiding’ them from users.
Nowadays, white fonting is an un-ethical SEO practice and I would never ever do it.
Here’s another thing I would never do: I’d never hide anything in white text about bookmarklets… I’ve said too much.