NOINDEX or FOLLOW for a site with thousands of subpages?

[Guest]

If you have a site with thousands of subpages (15% of the whole site, they are like an ad in an advertising catalogue, but you want to rank with category pages) which important for the visitors but you do not want to rank on them what you do? NOINDEX, FOLLOW?

[Mike]

Adding a noindex tag to any page that is a part of your site structure is a bad idea. It will cause the links to be treated as nofollow, which screws up your internal link structure.