readonly
Sets the read-only state of the input. A read-only input field cannot be modified (however, a user can tab to it, highlight it, and copy the text from it).
The readonly attribute can be set to keep a user from changing the value until some other conditions have been met (like selecting a checkbox, etc.). Then, a JavaScript can remove the readonly value, and make the input field editable.
Default value
False - the input is editable.
Valid values
True, False, or any valid XPath expression that returns a boolean value.