An HTML form with a read-only input field:
The readonly attribute is a boolean attribute.
When present, it specifies that an input field is read-only.
A read-only input field cannot be modified (however, a user can tab to it, highlight it, and copy the text from it).
The numbers in the table specify the first browser version that fully supports the attribute.
In XHTML, attribute minimization is forbidden, and the readonly attribute must be defined as <input readonly="readonly" />.