CSS stands for Cascading stylesheet. CSS is the language used for styling images. It is used to define styles for your web pages. CSS was developed in 1997 to allow web designers to define it to make web pages look good. CSS is used to design websites. CSS only works with HTML. HTML is just a markup language and you can use some attributes and values in tags, but you can't create responsive web page designs. The World Wide Web Consortium (W3C) has developed CSS to solve this problem. In HTML 4.0, all formatting could be removed from the HTML document and stored in a separate CSS file. Today all web browsers are supporting CSS.