The CSS Important Global Keywords are a set of keywords that are used to override the default styles of a web page. These keywords are used to ensure that a particular style is applied to an element regardless of any other styles that may be applied to it. The keywords are: !important,
From Wikipedia
Cascading Style Sheets (CSS) is a style sheet language used for specifying the presentation and styling of a document written in a markup language, such as HTML or XML. CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript.