Site Spider Traps

Avoid Spider Traps: Learn to Identify Site Traps

Check for spider traps on your website. These "mistakes" typically hurt your search engine optimization efforts by holding search engine spiders hostage. 

This happens typically with the use of relative links on your website.
Here is a quick illustration of several types of links used in HTML coding:

Absolute Link: http://www.filipecsantos.com/category/page.html
Full Link: /category/page.html
Relative Link (type 1): category/page.html
Relative Link (Type 2): ../category/page.html

The relative link type 2 is the one you want to worry about most, because if it is used on a page like an error page, it will likely lead to non-existent pages, creating an infinite loop for the search engine spider software to traverse - leading to a "trap" for the spider, in which most will abandon the site and not index anything. It's also important to note that the use of absolute links reduces the effectiveness that screen scraping scripts and software may have on most sites. If they do manage to scrape your content, most likely it will not benefit them much and will at least attribute a link back to your site (where applicable).

A secondary effect which is also negative is that these artificially generated links to additional non-existent pages will dilute Google PageRank (and other algorithms for Yahoo!, Bing, Ask, Etc.) so that the pages carry much less weight and are kept out of the index for ranking purposes. This counts if the pages you are trying to get ranked are generated from or within this trap site structure.