It's actually a very good website. I happen to disagree that it's the only explanation for flood channels on Mars, but it is certainly a valid and highly plausible option. It might have been good to have a little more about J Harlan Bretz and his adventures.

2 technical points:

The Wind arrows on the picture of Barchan dunes is the wrong way round - the "feathers" of the "moustache" point downwind

The Interior model of Mars is actually closer to that of the Moon. Although Mars has a thick cool crust, it is only 400 km thick or so, and a gently convecting mantle should lie between crust and core.

But for such a big website, that's not bad. I'm sure my own has at least as many serious errors (though it was nice to see Raoul link to it recently for Lowell's canals)!