"EXtensible HyperText Markup Language", or XHTML, is a markup language that has the same expressive capabilities as HTML, but with a tighter syntax. XHTML can be considered as the cross between HTML and XML in many ways, being a reformulation of HTML into XML. XHTML 1.0 became a World Wide Web Consortium (W3C) recommendation on January 26, 2000.

Basically XHTML is a modern replacement for the older HTML, being almost identical to the HTML 4.01 standard, an improved, stricter and cleaner version of the HTML 4.0 standard. Abstracting a bit, we affirm that XHTML represents an XML-type definition of an HTML document, in short a combination of HTML and XML. The benefits of an XHTML application are multiple: they can be read by all XML devices, while maintaining compatibility with all older or newer Internet browsers without requiring additional specifications. XHTML + TIME is an extension of the XHTML language, providing Web documents with support for multimedia timing and synchronization. Thus, using some new elements and attributes, an XHTML page can be added graphic, audio or video content, which can be synchronized with other elements along a time frame specified by the author of that page. The XHTML + TIME 1.0 version was first available in Internet Explorer 5, and currently XHTML + TIME 2.0 is recognized by Internet Explorer, versions 5.5 and 6.

benefits:

Web pages that have dynamic XHTML + TIME content can be used to add dynamic, interactive content to web pages. For example, web presentations can be created in the form of a slide show, within which text, audio, video or graphic data streams are synchronized. These presentations can be timed, interactive or combined.

Easy to use:

The facilities offered by XHTML + TIME bring a set of attributes and elements new to those already existing in the XHTML language, so that all previous notions of XHTML remain useful for designing web pages in XHTML + TIME. To allow easy use of multiple XHTML elements, they can be grouped into hierarchical relationships. The grouping can also be useful for specifying whether multimedia objects appear and disappear sequentially within the web page, or each has a timer independent of the others.
Support for scripting

The JavaScript or VBScript scripting languages further extend the flexibility and interactivity of temporal elements within web pages. XHTML + TIME offers a complete object model, which extends the current DHTML model, which consists of a set of properties, methods and events for adding interactive features to web pages.

XHTML + TIME elements behave differently when adding temporal attributes, depending on the type of the respective element. Thus, we distinguish two types of elements in the language XHTML + TIME: - content elements: all the elements that describe the content to be displayed on the page, including the new elements introduced by XHTML + TIME, which refer to multimedia objects (t: animation , t: audio, t: img, t: media and t: video). The most commonly used XHTML content elements are p, div, span, as well as table description elements. By adding XHTML + TIME attributes to a content element, a periodic occurrence of that element can be defined. - style elements: describes the display style for an element. Of the most used elements of style we mention: b, i and em. The attributes applied to a style element determine the attachment and removal of some display styles over time.