host 1accesshost.com/ down in Google

[bertham]

I handle about 100 websites, they all get high rankings in Google.
Four weeks ago 8 of my sites hosted by www.1accesshost.com dropped down from top 10 position to nowhere to find. I allready contact them, but they say "Don’t know why. Sometimes google does this. I have seen this in the past. Usually they come back, but I don’t know When.
Sorry,Matt"
Here is one site http://terra-vitalis.1accesshost.com/Can anybody help me to give me a reason for that. Has this something to do with hosting by 1accesshost?
Thanks for the help.

[TotalDesain]

I think, it caused by:
- search engine change his rule
- your web have going on static content for a long time
- your server down when search engine crawling your site. I got this message from your server:
HTTP Server Error 503
No available server to handle this request

[John Scott]

Are the sites interlinking?