:read-write

:read-write {
  /* ... */
}

<input type="text" value="Type whatever you want here." />
<input type="text" value="This is a read-only field." readonly />
<p>This is a normal paragraph.</p>
<p contenteditable="true">You can edit this paragraph!</p>

input {
  min-width: 25em;
}
input:-moz-read-write {
  background: cyan;
}
input:read-write {
  background: cyan;
}

p:-moz-read-write {
  background: lightgray;
}
p:read-write {
  background: lightgray;
}
p[contenteditable="true"] {
  color: blue;
}