Check it out Resource : http://en.wikipedia.org/wiki/Sandbox_effect you will be having the complete information.
its google criteria for new people, it like to judge before giving them a credit, and that is what we call sandbox, everybody have a sandbox.
I read that before indexing a site is sandboxed to check the content before it gets into the SERP. If your content is good I don't think it will be a problem.
Google sandbox is a place where a new site or the existing one put on hold their search rating because they rank poorly in SERP's. Webmasters do numerous things to take their website out from Google sandbox like frequent updation of contents, best keyword analysis and make their site search engine friendly. Whenever Google think that this site is worth to take out then that particular site should be taken out from Google sandbox.
The sandbox can be beaten easily with good enough inbound links. If you can get some high quality inbound links or some natural buzz about your site (or at least buzz that looks natural) then your site will start ranking quickly, regardless of how new it is. Also don't be afraid to link out. With new sites I've often seen the that the first pages to start ranking well are those that have good outbound links to high quality content elsewhere.
Its basically a theoretical "holding pen" for new websites. Until they build links and become "trusted" by Google.
There is NO SUCH thing as an actual sandbox place. SANDBOX is a concept someone developed when talking about the time it was taking Google to index their site. After that ONE person used this analogy the TERM stuck and people continued to use it. BUT IN REALITY, there is no such BOX. IT IS SIMPLY a waiting period, from the time a new site is submitted until it gets indexed. AND it varies from site to site. If your content is of HIGH quality and you build quality links your site will be indexed much faster than others. ON THAT same note, IF something shady happens with your site and there is some sort of doubt as to its originality, credibility and content Google may drop the index and filter your site out. If this happens then you need to analyze where or what has gone wrong. This often happens when any sort of Black Hat or Grey hat SEO practices are suspected. No Such thing as a penalty... You simply get filtered out. Change the content, continue link building, do ethical SEO practices and you will be loved by Google. The most coherent comment I have read on this thread. :0