How do sites know you've been there even when deleting a cookie?

Truss

How is it that some sites can still tell that you have been there before even though you delete your cookies?

Goodshape

This could be cookieless sessions on the server side. A value in their database which gets created when you visit, linked to your IP address and other detectable values (browser, OS, etc.). When you return the value is loaded and your options preserved.

Truss

Can it be gotten around? Changing IP address?

It seems to be a useful way of controlling who can login to an account - e.g. if you have an account where you download materials, by setting up cookiless session could you then set it up so that only someone logging in from the first time signup computer/IP address access the pages? A way of preventing someone just passing around their username and password?

Goodshape

I'm not sure exactly

Presumably you could go through a Proxy server, or otherwise spoof your ip address / location, to get past it.

One easy enough thing to try -- which might work -- is switching your modem off for a minute then powering it back up. Will likely get you a new IP address, which could be enough.

And be sure to also clear all cookies and anything else from your machine before going back to the website.

p

Flash has it's own cookies, it could be using that.

none

Using a different browser is the easiest option in most cases.