SitePoint har en god artikkel om spesifisitet i CSS:

Among the pages of arcane CSS lore you’ll find something called the CSS cascade; the thing that ultimately decides what each element’s style will eventually be. It has a reputation for being difficult to understand and is often the cause of those frustrating, obscure CSS problems when what happens in the browser is nothing like what you were expecting to happen. The amount of misinformation on the web certainly doesn’t help, so this is my small effort to correct the situation: putting to rest two of the biggest myths about the CSS Cascade.

Artikkelen tar for seg misforståtte kroker av CSS, som cascading, hvilken rekkefølge CSS-regler brukes, og hvilke selektorer som får presedens.