You know when your site seems to be running slow and you have done all you can to optimize it like use sprites and use cache, disable heavy plugins etc etc and you are stuck there watching your Firefox circle thingy go round and round and round and round when doing a simple task like saving a page...
Well, how do you convince your web host that it could be the server and not your site? Is there like a magical website somewhere on the web that you input your domain to see if it is performing on the server as it should?