How do websites BLOCK some users from their sites?

Question

How do websites BLOCK some users from their sites?

Answer 1

I'm no expert, but I think it has something to do with cookies.

Answer 2

Your linking program should be a hard working marketing tool of your business. It should bring you targeted traffic directly from your links, and in time it boost your ranking in the search engines and bring you even more traffic. This will be no cost targeted traffic, the best kind of traffic. However, if you are not selective in whom you link with your Blog, ranking can start to go down hill quickly. Avoid rinky-dink links and keep you Blog bustling along successfully

One way links, are of course the prize, but reciprocal links do need to be a big part of your Blog’s marketing program as well. Reciprocal links are much easier to obtain, but they do take some effort. There has been word about search engines and big marketers to de-value reciprocal links. The search engines are not crawling sites with a large amount of empty links. All links are good if they are well thought out. This means linking to sites of value and high page ranks.

With a new Blog, it may be harder to link to sites and Blogs with high PR. Look at the sit or Blog and see what it has to offer before you use this alone as a linking criteria. That low PR site may change fast in the future and bring you many visitors and search engine clout. Assess the site for quality content. Is it a site the search engines are going to like? Staying away from sites with scraped content, pages and pages of links instead of content and sites that are offensive in some way is prudent. {...}

More... http://dzesire.net/2007/09/14/avoid-rink...

Answer 3

There is a setting in the web server software that allows them to do this.