Are there general css paths for drupal
Drupal allows your site to have many Themes installed. Themes can define their own HTML structure to make your site look a certain way. Drupal has a few themes the ship out-of-the-box.

Depending on the theme you use it may or may not contain HTML classes or ids in the source to easily target specific items on the page. Typically, themes and Core html is fairly darn flexible.

Looking at the Zen Theme HTML and CSS markup you can see it has fairly specific rules to get at and theme alot of the content from Zen and also core drupal themes: Useful CSS selectors to add to your stylesheets