It’s also British slang for annoying.
I just looked up something in the online documentation for PHP. Pages are generally clean and usable as they appear in the browser, although there are a few poor practices if you look at the underlying HTML.
However. Take a look at a typical page. Below each formal section are (often useful) comments. Try moving the focus down the page different ways—scrolling, moving the mouse, page down. One comment at a time appears in dark colors. The other comments are pale and washed out until you move the focus to them. Then, over 0.4 seconds, they become opaque and readable.
And most of the goodwill from how well thought-out the rest is is squandered.
There is no reason to make text unreadable. And less still to waste the user’s time as they’re made readable.
Since transitions are new to CSS3, my guess is that programmers were playing. As they had in 1994 with
Playing is fine.
Then someone in the room has to say it’s great to know we can do this if we ever need it. But we don’t now. So take it out.