HTML scripting

The W3C HTML standard includes support for client-side scripting.
It defines how locally executable scripts may be used in a web page.
A particular client-side application, such as a web browser, may support several script languages.
Script code may be executed as the document loads or at a later time.

Script code can be written directly in the HTML document inside:
 SCRIPT elements
 Intrinsic event attributes

Script macros

Intrinsic event attributes 
Events occur for different elements of a web-page:
 Documents (BODY and FRAMESET)
 Forms
 UI elements (Anchor, Control Element, Image)

Script code may be associated with an event and element by writing code in an HTML attribute. The name of the attribute must be that of a supported intrinsic event for the element (for example, "onLoad"). The script is executed whenever the event occurs for that element. These scripts are mostly JavaScript. The HTML intrinsic event model consist of the following events:
Document
onUnload
Form
onSubmit
onReset
Document and UI elements
Focus
onFocus
onBlur
UI elements
Mouse
Movement
onMouseOver
onMouseOut
onMouseMove
Button
onClick
onDblClick
onMouseDown
onMouseUp
Keyboard
onKeyPress
onKeyDown
onKeyUp
Other (TEXT/TEXTAREA)
Lost focus with modified content
onChange (also OPTION)
Text selection
onSelect
Some browsers support additional event attributes (outside the standard), such as:
onResize
onMove
onScroll
onAbort

Script macros 

Netscape Navigator supported a feature called "JavaScript entities" or "script macros" by which script code could be included in HTML attribute values, using a syntax similar to that of  character entity references. For example, the code <img width="&{prompt('Width?')};" src="foo.jpg"> calls the JavaScript prompt() function to ask the user how wide the image should be.

The HTML 4.01 specification reserves a syntax for the "future support of script macros" in HTML attributes, but they have not been incorporated into later standards and are not supported by any current browser. A polyfill (entities.js) has been created in order to allow "script macros" in browsers that do not natively support this feature.

References 

Category:HTML
Category:JavaScript