Hover over either of the following 2 divs (depending on which image format your browser supports for cursors).
If cursor displayed (a radial gradient) is the same size as the gray area you're hovering over, the default object sizing algorythm is used to size the cursor. If the cursor is shrunk (to the size of a regular cursor), your UA is applying the MAY clause of CSS2.1's cursor sizing rules in section 18.1
You can use these to load a small cursor to check for generic cursor support, without getting into resizing issues.