Forget moogle, bahoo, lacevook or zwitter...world's most popular page is: 404 not found This page gets more traffic in one day than all described above get in 1 year...
If we could only harness that traffic The problem is that 404 is an error message and not a single page on the internet. So maybe you should say most popular phrase on the internet.
I do not think so because mostly website owners are going to remove this page from server so It could not be for long time.