Hi, I just tested all my jQuery selectors using the jQuery Tester (http:// jquery.nodnod.net), and the results seem to "contradict" one thing I read in a performance article: that you should descend from the closest parent ID when using classes in your selector (the article says "April 09", so the latest jQuery version was already available).
In my tests, using just the class selector (like span.myClass) was always fastest (sometimes twice as fast as #myDiv span.myClass), and this in all browsers I tested, not just the ones supporting getElementsByClassName. Maybe descending from the closest parent ID becomes a factor when you have a lot of elements on you page? Any experiences? Thanks