GML or General Markup Language was the first ever language these web developers used for composing web pages. It was influenced by Script which pioneered the concept of styles being separated from the marked up document. GML allowed for processing same source files to produce books, reports and electronic editions. A drawback of this language was it was limited to only document formats.
SGML or Standard General Markup Language was then introduced, which proved to be an intermediary for manipulating and exchanging text documents. SGML, in turn was used as a base for another language, HTML or Hypertext Markup Language, which allowed the developers to use fixed tags for composing a website. SGML’s more recent descendant, XML or Extensible Markup Language, allows users flexibility in terms of defining their own tags.