The goal of all standards is to ensure consistency. The standards which have been created for the web act as guides to building flexible and easy to maintain websites.
The World Wide Web Consortium, the W3C, is responsible for ratifying proposed standards. Web browser developers, such as Microsoft, are encouraged to build their products to conform to the W3C standards.
The ability to view the same content in the same way on different web browsers is the result of following these standards. This is the key to the enormous success of the web as a marketing and consumer tool over many other conventional means.