Citaat:
A PR4 web site, is a site where Google has given it a 'Page Rank' of 4. Page Rank is a logarithmic scale from 0 (new unranked/ poor ranked site) to 10 the theoretical maximum.
The highest sites such as Google, Facebook or the BBC have a PR of 9. Even the mighty amazon only has a PR of 8.
A Page Rank of 4 is a moderately popular site, with multiple links feeding into it from a variety of well ranked sites. It has probably been around for a little while and is reasonably popular in whatever niche it serves and possibly has a DMOZ listing.
Examples could be local companies that are successful in their niche, or forums.