Ruby on Rails
StyleSheets

Style sheets (also called Cascading Style Sheets or CSS) are a way of encapsulating the formating information of a web page (fonts, layout, colors, etc.) and separating it from the content (text, images, etc.). This has several advantages:

Rails style sheets are stored in your application’s public/stylesheets/ directory.

CSS Resources

category: Glossary

And how do you hook them into your applications?

So:HowtoCorrectlyUseStylesheetsInYourTemplates