Eric Meyer has kindly published some reset CSS styles, with the aim of overriding the browsers in-built default style sheet.
All internet browsers include a default style sheet which means that a web page without its own style sheet is not completely free from CSS styling as it inherits styles from the browsers default style sheet.
The reason why as web designers we might want to reset these styles is because there are various small and some not so small inconsistencies between these default styles from one browser to the next. Furthermore these default styles are controlled by browser vendors so there is no guarantee on their longevity and consistency in future versions and new browsers. It therefore makes sense that as web designers we should look to override these styles to prevent any browser inconsistencies and ensure long-term validity of our designs.