(Extensible Markup Language) is a markup language similar to HTML, but without predefined tags to use. Instead, you define your own tags designed specifically for your needs. This is a powerful way to store data in a format that can be stored, searched, and shared. Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. The World Wide Web Consortium's XML 1.0 Specification of 1998[3] and several other related specifications all of them free open standards—define XML. This course is dedicated to learn the basics of XMLDTD.XMLDTDstands for EXtensibleMarkupLanguage Document TypeDefinition.XML DTDplays an important role in web development field. For this reason, it is important for all webdevelopers to have a good understanding of XMLDTD. Before you continue, you should also have a basic understanding of XML,HTMLand Javascript. in this course you will learn the theoretical concepts of basics of XMLDTD.if you follow the course well it will be very easy for you to understand the concepts explained here.this is a beginners level course and this course is not for experts in XMLDTD