Hello!

I am just wondering as I work with several travel related pages, or so called city guides. One is for example the Krakow Guide at http://www.krakowguide.net/ . At the bottom of the page you can find links to other travel related city guides, such as Barcelona, Madrid, Budapest and so on. On the bottom of those pages you can find the same link system linking to the other travel related sites.

All sites have unique material, no copy-paste and so on, but I would just like to know if this kind of linking still can turn harmful to me in the eyes of Google? As I visited expedia.com I can see that they have something like the same system, but their page might work differently. Just curious, and hope to get some good insight from someone!

Link to WHO you want and HOW you want. Search engines will either count the links or not.
Linking to banned sites or sites that deliberately and blatantly attempt to subvert the search engines algorithms MAY cause problems.

Link Exchange rules also, when you talk, like you are a bridge, if their violation of the terms of search engines such as sites not viruses, adult content ..... you also considered the same range.
I think the exchange with the page content, which is the most recognized standard.

Linking to "adult content" is NOT a problem!!!

Do NOT confuse your morals or attitude with what Search Engines class as "bad neighbourhoods"

ya its very effected to your site because when google visit your page and its see a other site link means its a out bond link. Because of that its directly effected to your keyword rank.