hello.. i know from some forum that one site was targetting one most competative keywords and it was on the top in google SERP for a long time.but a'ter some time that site suddenly not shown.so how can we know that our site is there in sand box?? and why google putdown that top ranking site into sand box???? thanks
If your site has ranked for a phrase for some time and suddenly disappeared then it's more likely a penalty rather than the sandbox (which tends to affect newly indexed domains). What, if anything, have you changed on your site lately?