HTML accesskey attribute

What does this mean: "the v开发者_开发技巧alue must be an ordered set of unique space-separated tokens"?

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It means that the attribute:

• can accept multiple keys
• each key name (token) may not contain spaces
• a space must come between each key name
• you shouldn't use the same key name twice
• the order of the keys is important

I think accesskey in HTML 4 can only accept a single key character, but there is a proposal in HTML 5 for it to accept multiple characters (tokens) so if a device does not have a key for the first character specified it can bind the element to the next, and so on.