The <optgroup> element
Short for ‘Option Group’. A group of options within a <select> control, grouped together with a name in the user interface to make it easier for the user to find the option they want. These elements can't be nested, so there is only one level of grouping.
Full list of attributes
All the usual HTML global attributes are available
disabled- If this is set then the whole group of options will be disabled, as if they all had a
disabledattribute themselves. label- A textual label for the browser to use to describe this group of options.