Prison Google Sandbox
While the presence of the Google Sandbox has been long debated, Google has made no abject disclosure on the matter. However, as the sandbox effect almost certainly refers to a set of filters in play for anti-spam purposes, it is unlikely Google would ever provide details on the matter.
Google has long been aware that its historical use of links as a “vote” for ranking web documents can be subject to manipulation, and stated such in its original IPO documentation. Over the years Google has filed a number of patents that seek to qualify or minimise the impact of such manipulation, which Google terms as “link spam”.
As I know, Sandbox is one system made by Google to avoid spamming or black hat techniques. If your site is new and you are bombard of backlinks to get quick position on search engine, in this situation Google could place your website in sandbox. It would be good to promote website in natural way.
My experience, my website in 4 years with good keyword always in the first page on google http://www.baliholidayswedding.com, but after my site harm by spamming and we can’t clean it, google place our site in their sand box :(, after we clean all of harm on my site and send to google for review again our site, but until now we can’t exit our site from google sandbox.