This seems like a browser issue more than anything else. Yes it's "weird" to have millions of pixels horizontally on a page that is only a few thousand pixels tall, but it seems like an absolutely reasonable edge case that the browser should support.

I feel there's a joke here about "edge" cases from scrolling ridiculously long horizontal distances, but I'm not smart enough to make it.

And then it’s asking for Internet Explorer joke then, as an explorer something, not I’m not able to come up with it either.

“Why not save space by storing dimensions as uint16 internally?”

For the record, this HN page is already about halfway to overflowing uint16. The most popular HN page in the last day would overflow uint16.