The rel attribute defines a relationship between the linked resources (one being the document it appears on). And it provides that relationship with meaning, creating a semantic network where the different pieces have a role and a purpose. This detail may go unnoticed by most browser users, but not for the browser itself, assistive technologies, and web crawlers, which can take advantage of this attribute to provide a better experience. Also, savvy web developers can use it to make friendlier sites–we’ll see some examples in the following sections.