Cross-browser method for detecting the scrollTop of the browser window

Question

What is the best cross-browser way to detect the scrollTop of the browser window? I prefer not to use any pre-built code libraries because this is a very simple script, and

Answer 1

I've been using window.scrollY || document.documentElement.scrollTop.

window.scrollY covers all browsers except IEs.
document.documentElement.scrollTop covers IE.