Is it possible to find information about a certain person on the web?, let´s say

You cannot find personal emails in a search engine, unless they have been accidently published somehow, but depending on the person and their online behaviour, you may be able to find forum or group postings, like this. Lots of colleges publish their newsletters online and recent graduates are listed often enough. It also depends on if the person used their real name or a nickname online. Some public information (mostly based on change of address forms with the USPS, I believe) are also available at Zabasearch, see link below. Some court documents are also public record.

The only way I know is to pay for a background check. I'll check back to see if anyone knows where to go.