It's important to keep your
site up to date. Its content, security, whatever it is: you need to work
on it! While performing site maintenance, you could experience some
downtime. If it's for a short while, the chances of GoogleBot crawling
your site at exactly that time are slim. If it'll be longer or to be sure
when something goes wrong: check out this post by Jimmy! He explains how
to tell Google that basically, you're busy, and you'd like them to come
back sometime soon!
HTTP 503: handling site maintenance for SEO »
