I've been writing an ebook in html and css. I have an image-heavy section in my ebook, and occasionally in the Kindle previewer, images will be pushed to the next "page". That's fine. What I'm wondering is if there is a way to vertically center the content on the current "page" - instead of having all of the content at the top, and a huge blank space below. Is there a css class or pseudo-class that applies to the content currently displayed or something like that?