Elements of a web page

A web page, as an information set, can contain many kinds of information, which is able to be seen, heard or interact by the end user:
Perceived (rendered) information:
Textual information: with diverse render variations.
Non-textual information:
Static images on raster graphics, typically GIF, JPEG or PNG; or vector formats as SVG or Flash.
Animated images typically Animated GIF and SVG, but also may be Flash, Shockwave, or Java applet.
Audio, typically MIDI or WAV formats or Java applets.
Video, WMV (Windows), RM (Real Media), FLV (Flash Video), MPG, MOV (Quicktime)
Interactive information: more complex, glued to interface; see dynamic web page.
For "on page" interaction:
Interactive text: see DHTML.
Interactive illustrations: ranging from "click to play" image to games, typically using script orchestration, Flash, Java applets, SVG, or Shockwave.
Buttons: forms providing alternative interface, typically for use with script orchestration and DHTML.
For "between pages" interaction:
Hyperlinks: standard "change page" reactivity.
Forms: providing more interaction with the server and server-side databases.
Internal (hidden) information:
Comments
Metadata with semantic meta-information, Charset information, Document Type Definition (DTD), etc.
Diagramation and style information: information about rendered items (like image size attributes) and visual specifications, as Cascading Style Sheets (CSS).
Scripts, usually JavaScript, complement interactivity and functionality.
Note: on server-side the web page may also have "Processing Instruction Information Items".
The web page can also contain dynamically adapted information elements, dependent upon the rendering browser or end-user location (through the use of IP address tracking and/or "cookie" information).
From a more general/wide point of view, some information (grouped) elements, like a navigation bar, are uniform for all website pages, like a standard. These kind of "website standard information" are supplied by technologies like web template systems.