I made a good chunk of change with a similar method to 'hidden text' back in about 06 / 07. Here's how it worked.
I signed up at the 'meatcash' affiliate program, which if you remember were very 'extreme' sites for the time - 'Meat Holes' and 'Piss Mops' etc... I then downloaded the page that was 'Sites you can promote' which was graphically showing the sites in a pre made professional way. I then replaced all the links with my affiliate links, (cloaked) and stripped all the other metadata out of the screen. As it sood, there was no reference to anything at all, no text, no image names, nothing. Just the grid of sites with my links in it... For all intents and purposes an empty page with no descriptive text at all.
Then I googled 'Extreme Porn' - 'Banned Porn' - 'Illegal Porn' - Corrupting Pornography' - etc etc... You get the idea, then took large chunks of text out of the top three results that google gave me. These results were not stes promoting this type of pornography, but complaining about it, rallying against it, and trying to get it banned in the UK etc etc...
I saved all this text and mixed it up a bit and then added it below the images with my links. I left a bit of space first, then posted my text, nicely formatted using paragraphs and indents and all spelled correctly etc, including all the relevant anti porn links to government entities and national newspapers etc, under the images and links in a slightly different shade of blood red than my actual blood red background.
It seemed to work, because google did not seem to see my images, but did read the text that was underneath, so to google, I was a site that was actively campaigning against extreme pornography. I was an 'anti-porn' site, in google's eyes...
As such, after a while, when someone typed one of my originally searched phrases, I was right up there at the top, sometimes above the legitimate antoi porn sites that I had swiped and manipulated the text of, and I started getting A LOT of traffic !
Naturally, when you search 'extreme brutal porn' that's what you are looking for, and these days, its what google will give you, with page after page of pornhub links, but back then, it assumed that you wanted to be against it, so it served my site instead !
All my text was on the graphics so unreadable to google and all it saw was my 'anti porn' text that went on for ages and ages, but the real people just say a girl getting 'Fished Hooked' while some dude took a piss into her gaping asshole...
I made a pretty penny back then... Thus ends my trip down memory lane to 'The Good Old Days...'
