So why am I messed up because a lot of my websites have more than half of their pages shown as supplemental pages ?
Google has more than half of it’s index, as supplemental too. You gotta’ love them right ? ;)
What are supplemental pages ? usually outdated, non-existant pages that hang on in the SE’s with an old cache date. About every website out there has them. Supplemental pages can also mean pages that are considered duplicate content eg. pages that don’t reflect enough fresh and unique content to be considered stable pages.
In the past, if someone had half of the website’s indexed pages as supplemental he really must’ve did something really bad. Now, this is just a day to day routine.