I'm almost finished rewriting the website for a non-profit organization. The existing site receives ~5,000 a month. The new site is being written in ASP.Net and the existing site is PHP. The current hosting provider does not support .Net hosting, so I'll be switching providers.
My question revolves around the transition from the old site to the new. I would really like to get the new site up at the new hosting provider and do thorough testing before changing the DNS records for the domain.
Question: How can I put the new site up, test it, make any changes/additions necessary before updating the domain DNS to point to the new IP without Google indexing the content? Also, what SEO repercussions should I be aware of when making such a drastic change to the content that exists under the domain name?