Feet in the oven, head in the fridge?

The most amusing demolition of statistical tripe may be the joke that if my feet are in the oven and my head in the fridge my temperature may be on average normal.

I was reminded of this on seeing that web expert Gerry McGovern says the ideal length for a page on a regular web site (not a landing page) is 300 words. 50% of visitors will read all a 300-word page, but only 5% will scan 1,000 words.

"Ideal" meaning what?

The question is, which readers will read the longer copy; and which the shorter? And which among them will be most interested? No prizes for guessing - and heaven preserve us from experts.