XHTML a reformulation of HTML so that it conforms to the rules of XML. XHTML is similar to HTML but combines the flexibility of XML
PHP, a scripting language designed for producing dynamic web pages. It can include a command line interface and work with graphical applications. Created in 1995, PHP is free software released under the PHP License, PHP is a widely-used general-purpose language suited for web development and can be embedded into HTML. PHP is installed on over 20 million websites and 1 million web servers. PHP allows input from a Web Browser to your Web Site and to control other functions.
Cold Fusion an application that creates HTML pages from a database. Cold Fusion, for instance can create a template that is defined, that a user enters information for use in gathering data. A catalog, for example, is easy to build and maintain in Cold Fusion. Cold Fusion is from Adobe/Macromedia.
Cascading Style Sheets describe how a web page or other document is presented on the Web. CSS can be written for different media, can be part of an HTML document, or can be a separate file that is applied to multiple HTML documents.
Perl a general-purpose dynamic programming language. Perl developed in 1987, it has undergone many changes and revisions and become widely popular among programmers. Perl borrows features from other programming languages including C, shell scripting (sh), AWK, and sed. Perl provides powerful text processing facilities without some of the past limits. Not the mainstream today but we are fluent in Perl all the same.