yeah i want to know this too! from what i can tell you have to pay to be listed by netcraft, so it seems pretty biased....i'd rather pay for an objective analysis of hosts.

There are statistics out there from other companies, but none -- it seems -- as much of an authoriy as Netcraft.

>> how hard it is to replicate what Netcraft does?

I'd say it would be pretty difficult. It's not just the collection of data that's difficult, but WHERE the data is collected that seems to be a larger issue. I know Netcraft has a large client base that includes many large companies, including hosting companies.

>> How to figure out how many servers are behind a website?

I'm sure there are various methods of doing so -- none that I am familiar with. However, examining hosting companies is a good start at estimating this IMO. I'm sure they get stats from ISPs, as well. It's just a mass collection of data from various sources compiled together, I guess.

>> is they're methodology way off?

It depends on how they make their hypothesis and extrapolate their data. All statistics have certain percent error and this can vary depending on many, many factors, including data collection methods, as mentioned by rubing. If the statisticians did their job well then the stats should be relatively accurate.

>> pay to be listed by netcraft

Don't think that's true?

Thanks, eelixduppy....

I guess Netcraft must be pretty unique -- since I can't seem to find any other service that does what they do. They do seem to have some advantages by having a toolbar and large customers that can help add to their data collection methods. But I'm not actually sure how they use their toolbar to help gather information....?

>> toolbar

It grabs information about the websites you are visiting and sends the data back to a server somewhere. From the FAQ:

We do, however, collect the names of the web sites visited by our users in order to provide popularity ranking information and contextual reports for the site being browsed.

[toolbar.netcraft.com...]