Cloaking is the act of sending different data to search engine crawlers than to users of a page. You can usually see cloaking in action on shady sites that have a bunch of keywords at the bottom of a page that are the same color as the background text. In the end, those keywords aren’t part of actual content, but designed to inflate search engine stats. Cloaking in the age of Google also involves linking those keywords to increase Page Rank, the stats by which a page moves up or down in Google.
Cloaking is something that search engines frown upon and even ban you for. Yahoo, according to a blog, has actually been caught cloaking.
Below is what you, as a user see (click to embiggen):
And here, below, is what a search engine crawler sees (click to embiggen):
He also points out four ways in which Yahoo! is violating its own guidelines for sites:
# Pages using methods to artificially inflate search engine ranking
# The use of text that is hidden from the user
# Pages that give the search engine different content than what the end-user sees
# Pages built primarily for the search engines
Not Good, Yahoo!. Not good at all.
via Threadwatch
