is top.document cross browser?

I'm writing a javascript that relies on top.document but I'm not sure if I can assume all the major browsers supports it or not.

Is top.document cross-browser compatible?

From stackoverflow

• According to W3Schools, window.top is supported in IE (since v4), FF (v1), and Opera (v9). I can personally vouch for it working in Safari as I just tried their example code in my own browser. :-)

• I've never used it, but I believe it is.

  Nested frames are so passe.

  Check out this handy Quirksmode article on the topic.