Just try to make sure you've found the real website and not one of Grubhub's autogenerated fake sites. They all look pretty similar so you'll be able to identify them after you've seen a few, but it's easy to mistakenly think you're at the real site the first time.
There's nothing to keep Grubhub from changing their site design. And someone else might get the same bright idea. So learning what a fake site looks like isn't going to be a long term solution.
I wouldn't say "most". The small local restaurants that you really want not to get taken by predatory schemes are the ones least likely to have a web presence.
