It's not always a bad thing; for something like API docs, a fixed header can make sense. But for blogs and brochure-ware, and even some web apps, it breaks the

It's not always a bad thing; for something like API docs, a fixed header can make sense. But for blogs and brochure-ware, and even some web apps, it breaks the focus on the content and steals precious screen real estate. If the most common use case involves many quick jumps across the page hierarchy, fixed header can be a good fit (though an affixed side-nav might be better for wide screens). But if the most common case is drilling down to a specific page and spending a little time there, then fixed headers just create noise and get in the way.