A pre-selected <command> element:
The checked attribute is currently not supported in any of the major browsers.
The checked attribute is a boolean attribute.
When present, it specifies that the command should be checked (pre-selected) when the page loads.
Note: This attribute can only be used if type="checkbox" or type="radio".
The <command> tag is new in HTML5.
In XHTML, attribute minimization is forbidden, and the checked attribute must be defined as <command checked="checked">.