What do Satanic websites like black backgrounds with red letters being the majority of the website?

I COMPLETELY agree, and I'm a Satanist. I don't mind a black background if the font is at least clear. It's better for your monitor than a white background anyway. I'm all for aesthetics, but not at the complete sacrifice of practicality.

I made my website with a yellow background, if it's any consolation to you.

EDIT: Somebody here claimed that there's "iffy background" about Anton LaVey. The accuracy of LaVey's biography is simply irrelevant to the validity of the religion. We're not a cult. People trying to use fallacious ad hominem attacks like this against Satanism are no better than those creationists who try playing the "Darwin recanted on his deathbed" story.

Try The Satanic Bible by Anton LaVey

red/black are suppose to be "evil" colors

someone already said anton levey, but be warned there's a lot of iffy background stuff about him, But the Satanic Bible by him is a great start, it's basically a pretty good read. Also try the prince by Machiavelli

The Prince of Darkness finds that color scheme very soothing. If they go with anything different then He may turn His back upon his unfaithful followers.

Quite a few valuable answers here

Visual appeal to silly people.

Atheists are purveyors of a wicked plot

"Six things there are, which the Lord hateth, and the seventh His soul detesteth: haughty eyes, A LYING TONGUE, hands that shed innocent blood, a heart that deviseth wicked plots, feet that are swift to run into mischief, A DECEITFUL WITNESS THAT UTTERETH LIES, AND HIM THAT SOWETH DISCORD AMONG BRETHREN."

Prov 6:16-19