As any search engine, Google has a filtering system to his extradition. At Naveen Selvadurai you will find additional information. A large percentage of sites on the Internet is not created for people, and to redirect traffic to other sites to influence search results, etc., hence issuance of a search engine that was clean, the garbage must be carefully filtered. Filter so as to not hurt the normal sites. But there are no clear criteria for 'normality', so the problem of filtering is complex, and it is still not completely solved. Under the filters often become 'white and fluffy' sites and reasons for falling can be very difficult to define.
Analyzing information about the filters (and can be analyzed only Webmasters opinion, as he puts Google does not practically no information about its search technology), clearly shows that the names of many filters, but they all boil down to just one – honestly unraveled, and the site will be all right. Therefore, it makes no sense to determine with high accuracy, as is imposed on the site filter. Ways out from under them are about the same, and knowing the names will change nothing. 1. Sandbox, sandbox. Filter, faced by the majority of young sites.
Manifested in the fact that the first months of the site, it essentially can not take first place in the issue, in any methods of site promotion. Sandbox – this is not a sanction, it certain probationary period for young sites. The reason for its introduction, most likely, was the desire to weed out short-and doorways to prevent their presence in leadership positions in the search results.