This was extra sketchy from the very beginning. Here’s how it worked… The webmaster/SEO’er would add a bunch of keyword laden text to the page and make it the same color as the background, thus seemingly invisible to the visitor. White colored text on a white background was the most common.
This was one of the original “black hat” techniques, and it evolved every time the search engines caught up – for years! This was the turning point when search engines decided they had had enough of unscrupulous optimization tactics. Here’s what happened…
As you already know, the search engines said “enough of this” and banned the use of so called “invisible text”. Google and the other big players initially thought this would be enough to reduce the majority of the abuse. Boy, were they in for a surprise!
Greedy webmasters and SEO’ers decided to play it fast and loose by looking for loopholes in the color palette. And they found plenty. They knew that search engines cannot ‘see’ color. They can only read color codes. And with 256,000 colors and shades in the (then) current spectrum, many decided to get around the system by using a color that was simply a shade off, but virtually indistinguishable to the human eye. A common example seen in millions of pages was two shades of green, identified by hex color code ID’s #66FFFF and #33FFFF. They look 99.9% identical to the human eye but search engines interpreted them as totally different colors – for a while.
Once major search engines caught on to this scam, they started spending hundreds of thousands of dollars in developing technologies that could tell when invisible text was being used based on spectrum analysis.
Classic Rule - 1.3 Visibility = Transparency
Search engines can tell when you are trying to keep things hidden from your visitors, so don’t bother. Be transparent. Be REAL. They see “invisible” text as cheating the system and will punish your site if they catch you at it. And don’t think for a minute that your visitors are oblivious. This trick is so old that just about everyone knows how to spot it by highlighting big blank areas and watching that hidden text come to life.