Web pages are plastic in both horizontal and vertical dimensions in a way that paper pages are not. Therefore, even before you decide on a page grid, you need to decide on the fundamental page framework that suits your site best: a fixed-width page or a flexible-width page.
Deciding on page length is easier. Here the best practice is a common-sense approach that works well for your content. The old saw that “web readers don’t scroll” may have been true of new users a decade or more ago, but it certainly isn’t true now. As readers have grown used to the web as a reading medium, the design constraints on page length have lessened, and usability studies have shown that web readers certainly do scroll through web content that interests them.