toggle Toggle Switch

Specifies if the styling of the element it modifies should act as a toggle-switch. When the toggle-switch is on, the textual content of the element will always be visually set apart from its context. When the switch is off, the rendition is fixed to the style requested and will not change based on context.
OPTIONAL (defaults to yes) on element: <italic>
Value Meaning
no The element does not act as a toggle; the emphasized text remains in the requested style, no matter what the surrounding text does.
yes The emphasis element acts as a toggle. If the surrounding text is set to the same emphasis style, the text within this element will change to another emphasis style, so that the text will always be typographically distinct from its surroundings.
Default value yes
OPTIONAL (defaults to no) on element: <roman>
Value Meaning
no The element does not act as a toggle; the emphasized text remains in the same emphasis, no matter what the surrounding text does.
yes The emphasis element acts as a toggle. If the surrounding text is set to the same emphasis, the text within this element will change to another emphasis style, so that the text will always be typographically distinct from its surroundings.
Default value no
OPTIONAL on many elements; click for list and usage
Value Meaning
no The element does not act as a toggle; the emphasized text remains in the same emphasis, no matter what the surrounding text does.
yes The emphasis element acts as a toggle. If the surrounding text is set to the same emphasis, the text within this element will change to another emphasis style, so that the text will always be typographically distinct from its surroundings.
Restriction This is an optional attribute; there is no default.
Tagged Sample

Overline Q will remain overlined in all contexts

...
<p>As Q and <overline toggle="no">Q</overline> are always 
different ...</p>
...