I was just reading over on Dave Ferguson's blog that he used custom CSS to change the modal mask color of the elements rendered using ColdFusion 8's new CFWindow tag. This brought up a very interesting thought in my mind - is this something that anyone should attempt to do?
Here's my thinking: the rendered XHTML and CSS are part of ColdFusion 8's underlying and undocumented implementation of the new layout and AJAX features. To me, this is right on par with the Java functions that are also undocumented yet available on all ColdFusion objects. There's nothing here to say that the next HotFix or the next ColdFusion upgrade won't completely change the way the XHTML or the CSS is written (and therefore break any overriding CSS rules you have).
Now, the slight difference here is that if the CSS changes in an update, the site won't break functionally, whereas if the underlying Java implementation changes, a site may very well stop working (if it references those formerly available Java methods). While this might sound like a large difference, I say "slight" since both of them would require a developer to manually fix code (and at that point, the difference in update time is probably only minutes vs. hours - not a huge deal in my mind if it's part of a system upgrade).
That being said, I am NOT saying that Dave is wrong or that you should ignore the available, underlying implementation; to the very contrary: I am one who believes that harnessing the power of underlying features is a good thing (and is really only just one more thing to consider when upgrading a system). I am just wondering what people's thoughts are on this - sometimes it is easier to formulate opinions when the example is more tangible (CSS vs. Java).
All in all, I assume that the people who oppose calling underlying Java methods will also oppose adding your own CSS overrides, but I am curious.