4.12.7 METHODS attribute

This attribute is optional. If present its argument is a space separated list of HTTP METHODS supported by the object and accessible to the user.

These are more accurately given by HTTP protocol header messages (the server sends this information, along with the data you requested, as soon as you select a URL), but it may be useful to include the information in advance in the anchor reference. For example, the browser may chose a different rendering as a function of the methods allowed (for example something which is searchable may get a different icon). Unfortunately, there are no browsers that do this.