Link relations is a way to explain why a resource is be linked to as well as build an understanding of the relationship between data. Common uses of link relations in web design are linking to a stylesheet, image or a javascript file. HTML5 expands the concept of link relations even further by adding more categories to the vocabulary. By categorizing a link ( rel="" ), a web designer is able to tell the program interpreting the code how to process it.
There are two types of link relations:
Example of the most common uses of HTML link relationships:
<link href="main.css" type="text/css" rel="stylesheet" />
There are quite a number of classifications for links. From specifying a usage to creating an understanding of directional navigation, the REL component of a link can provide helpful meta data for a browser or an application.
Navigational relationships:
Other examples:
You can also use such meta data (or microformats) to provide an understanding of a relationship between people as well: