If this text string is green, your browser supports child selectors (>).
If this text string is red, your browser supports a specific combination of id and child selectors (e.g. #foo>#anotherfoo). (update: or at least, gives the impression it does)
Update:
This third paragraph (id is test3) has a div wrapped around it and thus is a child of a child of div id="main". As the style rule #main>#test3 {color: orange;} should not be applied, the paragraph is supposed to be black.
Conclusion: IE5.0/Win ignores all (selector) information before the #. In the last example, it skips over #main> and thus colors the paragraph orange.