HTML and CSS Reference
6.7.2. The <link> Header Element
Use the <link> tag to define the relationship between the current docu-
ment and another in a web collection.
The <link> tag belongs in the <head> content and nowhere else. Use the
attributes of the <link> tag like those of the <a> tag, but their effects
serve only to document the relationship between documents. The <link>
tag has no content, and only XHTML supports the closing </link> tag.