Having a new website can be an exciting time but it can also be worrying especially if you currently have some great rankings. Launching a new site can see a temporary dip in your search engine rankings but this should come up again quite quickly once the site had been reindexed. The problems occur when there are parts of the site that are not working correctly or page redirects and permissions have not been set up as they should. If for example a robots file has been set up on the server asking the search engines not to index the site due to it being in development, and this file is not update when the site goes live you may find that the majority if not all of your URL’s do not get indexed. If they are not indexed then they will not show up in the search engine results pages and therefore your rankings will drop down. This can often be seen in a sudden drop in traffic to.
Although this is easy to rectify, it is not easy for you to get Google or the other search engines to revisit the site. You can request this but it may take a lot longer than you would like it to.