Current Definition of the activate Attribute
3.1.1. activate = ( yes | no )
The activate attribute indicates whether a target element should be activated or not once it obtains focus. The default value for this attribute is "no", indicating that the element will not be "activated". User agents MUST provide mechanisms for overriding the author setting with user-specified settings in order to ensure that the act of moving content focus does not cause the user agent to take any further action (as per Checkpoint 9.5 of UAAG 1.0).
User agents MUST provide keyboard mechanisms for "activating" any event associated with the focused element (as per Checkpoint 1.2 of UAAG 1.0). User agents SHOULD make available the list of events associated with the focused element (as per Checkpoint 9.6 of UAAG 1.0).