But how you link them together can also have an influence on ranking. It is better to use text links instead of graphics or button/image links. That way you can use your keyword in the link. If you decide to use graphic images for your navigation be sure it is not done with an image map, unless you have some other navigation method as well. Many search engines cannot follow the links in image maps. Using the Alt attribute on images is believed to add a ranking boost for some search engines, but don’t just use it stuff your page with keywords, this will not make the search engines happy.

How do they affect PR? The main concern with outbound links is the possibility of having too many links and the search engine mistaking your site for a “link farm” and therefore penalizing or even banning it.  To avoid this possibility, Google recommends no more than 100 links on your site. Natural, one way, theme relevant links are the best links for PageRank building.

Also important is the destination of those outbound links. While no website owner can control who links to their site, they can control who they link to. There are sites that are considered “bad neighborhoods” and the search engines frown on sites linking to them. Google's published Webmaster Guidelines describe this practice as a "linking scheme" designed to trick the search engines, and any sites found linking to them are therefore subject to penalties and/or banning. The most well known bad neighborhood is the “link farm”.