HTML The Definitive Guide (133 page)

Authors: Chuck Musciano Bill Kennedy

BOOK: HTML The Definitive Guide

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If you don't include a src attribute with the tag, you've got to include a type attribute to explicitly reference the MIME type and hence the plug-in application.

13.2.4.7 The type attribute

Use the type attribute in addition to or in lieu of the src attribute. Its value explicitly indicates the MIME type of the embedded object, which in turn determines which plug-in the browser will invoke to process the object. This attribute is not required if you include the src attribute and the browser can determine the object type from the object's URL or server. You must supply a type attribute if you don't include the src attribute.

It may seem odd to use an tag without a src attribute reference to some object, but this is common if the plug-in requires no data or retrieves its data dynamically after it is started. In these cases, the type attribute is required so that the browser knows which plug-in to invoke.

13.2.4.8 The units attribute

The default units of measure for the height and width attributes that control the display space is pixels. The units attribute lets you explicitly state that the absolute measure is pixels, or change it to the relative en, which is one-half the current point size of text in the document. With the en units, you tailor the object's viewing area (viewport) to be proportional to its immediately surrounding content, the size of which is varied by the user.

For example:

creates a view port for the window 200×320 pixels. By changing units to en, that same view port, when included within a flow of 12-point text, will become 1200×1920 pixels.

13.2.5 The We recommend using a