Consistency is an important principle of web design.
It can help bring a degree of uniformity and familiarity to a website which represents your brand and culture. Keeping fonts, font sizes, heading, subheadings and button styles consistent will help user interaction and site navigation.
Visitors will know what they’re looking out for and will be able to easily skim read a page.
This is how people tend to consume online content.
CSS or Cascading Styles Sheets is a style sheet language used in web development. CSS describes the presentation of a document written in HTML or other markup languages.
A good implementation of CSS makes creating consistent websites much easier.
CSS allows you to describe the styles of all elements of a website without having to add the format individually to each element which can result in mistakes.