At the office we have 4 mbps download and 512 kbps upload speed. Is this enough to host a website? And how fast are the upload and download speeds of sites like youtube, ebay, etc. Thanks!

It depends on how much content you'll have on your web site. If it's graphic intensive, it's probably not going to be enough, but if it's only text based, it'll be fine for now. It also depends on how many users you expect to be using it at the same time, if you plan on allowing remote access to your systems, and other connections to you from the outside. It would not be unusual for a site like E-Bay to have multiple DS-3's or OC-3's from multiple ISPs so that they can do load balancing across them. These are large sites though, so there's not much sense comparing them unless you plan on becoming the "next big thing." There's some stats at the bottom of the link below, but it doesn't really tell their actual bandwidth from their providers.

WG