How critical is the Supplemental Index today?

[Sarah Atkinson]

I just checked my 4 sites have a supplemental index of 12.5%, 89%, 94%, 93.5%

Just how bad is that?

[tedster]

Well, as one of our currently featured threads reports, Google has just changed the way they search over the Supplemental Index, and more pages are now showing up in the SERPs, even though they are in the supplemental index.

Supplemental URLs Now Ranking in Google [webmasterworld.com]

However, I would consider 90% plus to be a sign of something being not quite right - check your site for things like Duplicate Content issues - especially two or more urls that are different in some way, but still resolve to the "same page". There's a good selection of Duplicate Content threads in our Hot Topics area [webmasterworld.com] that can help you with that.