I have noticed for years now that when I spend any more than about a minute reading something on the Memory Alpha website (a Star Trek wiki), I temporarily see horizontal lines in my vision that last a few minutes.
Does anyone know what it is on the website that is causing this side effect? It is annoying enough that I avoid that website whenever possible, although it is sometimes necessary to visit the site when answering questions on SciFi.SE.
I'm assuming that it is something in the background, but I'm not sure if it is a background color, an image, the text color, or some combination of those. If I can identify it, I might be able to set up a user stylesheet in my browser to filter it out.
I will add that I spend a lot of time on my computer, and that particular website is the only one I've ever noticed having that effect on me.