If he uses an Apple product, the answer is obvious: Safari!

Because it is preinstalled and Chad does not bother about something like a web browser. And honestly Safari is also a good enough browser for OS X.

And for Linux he would probably just use Firefox, which is preinstalled in most distros except for neckbeard distros like Arch.

But for Windows? On one hand he should use Internet Explorer because he does not bother about installing a new browser. But on the other hand other web browsers are so much better. Maybe he goes for the alpha version of Chrome or Firefox. The stable version is more for the provider kind of guy anyways.