Here are some explanations:

Cookie Tracking
This method works by writing a small text file, a "cookie", to a user?s browser when they click on an affiliate link. This cookie holds the referring affiliate?s ID, which can be identified at the merchant?s order page to credit affiliates for referred sales.

Hit Counters
Where you use a small piece of script on every page like Sitemeter, extreme etc

CGI / URL Tracking
A Perl script or JavaScript which (1) reads the current URL, (2) grabs the affiliate ID, and appends it to the URL of the next page.

Other:
Any other method of tracking

Using activemeter.com. For something that's free it has some neat features. statsmachine.com is very good as well but there's a $30 yearly fee (worth every penny if tracking visitor is important for you).

Thanks for that Trippler, can you sort in various formats, archive etc?

I have a hit counter..2, actually, only on the first page of my site.

I use a hitcounter, although I think it tracks cookies as well. It gives me very detailed information about visitors to my site - what browser they use, operating system, country, etc.

And it's free, so it's all good.

Not sure what you mean by sorting in various formats. But the details of your visitor (particularly statsmachine) is quite comprehensive. For visitors that get to your site via google or any other major search engine they'll even tell you what keywords was used by the visitor. All columns are sortable with the added option of filtering specific details. Try it, there's a 30 days free trial and you'll see what I mean when I said it's worth every penny of the $30 that they charge you.

I meant can you sort by IP, keyword, SE, date, etc which you answered, thanks :-)

I did the poll out of curiosity, I was wondering how many track the visitors through their sites or for ads sent, traffic exchanges, spam or illegal activity etc etc

Use those two to track ads that I send out and also to track illegal bot like activities.

Quite frankly I'm fed up with sites that sell 5000 hits but only end up sending 500 and the only excuse they can give is that the counter that I use is not able to track the "huge" amount of visitors that they claim to send. Either they know nothing about the business or their just a bunch of cheats. But at least with these counters I don't end up being a repeat visitor

Ditto :-)

I use Sitemeter to track hits to my ad and info pages, which is both free and gives decent info on who came to your page.

For my traffic exchange, I track everything! Just the usual P.O. paranoia and protection against those that think I'm actually as dumb as I look.