1. Style solves the common problem:
Different browsers act differently to documents, so W3C standardized CSS standard that is supported by all major browsers.
2. Stylesheet can save a lot of work:
Font and Style attributes of HTML are used to format the document, so we define them using CSS in a separate file, by changing at one place we can modify our entire website pages.
3. Multiple style cascade:
Style can cascade into many ways i.e. into a single element, head or external files.