What is the HTML DOCTYPE Declaration or DTD?
According to HTML Standards, each HTML document requires a document type declaration (DTD). This statement starts the document declaring what language version the document uses for proper viewing in the web browser or user agent. To ensure correct viewing of a document on all user agents the document type declaration is strongly recommended. Though most web browsers will display basic web pages correctly without a proper DTD. The DTD is the first tag in an HTML document. Example of a DTD: .