One of the biggest annoyances I ever see in a website’s source code is layers upon layers of complexity. 20 nested <table>s, 30 nested <div>s – what’s the difference? Building a consistent and semantic website isn’t just an issue of whether or not you’re using valid code or mistreating a poor table by filling it with non-tabular data – it’s a question of whether you’re using logic to decide what element should be used to represent your content.
How deeply does a piece of information actually need to be buried in your document? Well, optimally (and arbitrarily), no more than 7 layers: