[hirako2000]

That's called search: in history.

[hoppyhoppy2]

That doesn't search the content of the pages you've browsed, though, right?

[hirako2000]

Right, I misunderstood the case.

I guess because it isn't then trivial for a web browser to do, indexing every text ever rendered?

[packetlost]

I think you would need to take it a step further and do full-text search on loaded pages. It's certainly possible but probably pretty data intensive.