A custom CSS pointer is what it sounds like.
why does it do that only when over hyperlinks?
No, it's built into the OS. I don't know what it is either. It's like the spinning beach ball, but it doesn't spin and it's just different colors of blue. It sits next to the mouse and only happens when things are loading and I hover over certain objects. Anyone know what it means?
One thing I have noticed that is quite annoying in OS X is there are four or five mouse pointers that all basically mean something is loading. Really inconsistent and very annoying.
it did a lot on facebook and few other websites, but it's only occasional, doesn't always do it.