[yaseer]

Yes, very good question (I've answered a similar one on detecting whether the page has finished loading).

It's a deceptively hard problem. Essentially, what we do is fingerprint the element. If the page changes, it boils down to how effective our fingerprinting and search algorithms are, to find the element if it has moved or changed.

The algorithms behind that are good enough for most use-cases now, but it's something we're continuously iterating on.