13.8 How to specify alternate text

Attribute definitions
alt = text [CS]
    For user agents that cannot display images, forms, or applets, this attribute specifies alternate text. The language of the alternate text is specified by the lang attribute.

Several non-textual elements (IMG, AREA, APPLET, and INPUT) let authors specify alternate text to serve as content when the element cannot be rendered normally. Specifying alternate text assists users without graphic display terminals, users whose browsers don't support forms, visually impaired users, those who use speech synthesizers, those who have configured their graphical user agents not to display images, etc.

The alt attribute must be specified for the IMG and AREA elements. It is optional for the INPUT and APPLET elements.

While alternate text may be very helpful, it must be handled with care. Authors should observe the following guidelines:

    * Do not specify irrelevant alternate text when including images intended to format a page, for instance, alt="red ball" would be inappropriate for an image that adds a red ball for decorating a heading or paragraph. In such cases, the alternate text should be the empty string (""). Authors are in any case advised to avoid using images to format pages; style sheets should be used instead.
    * Do not specify meaningless alternate text (e.g., "dummy text"). Not only will this frustrate users, it will slow down user agents that must convert text to speech or braille output.

Implementors should consult the section on accessibility for information about how to handle cases of omitted alternate text.

7.4.3 The title attribute

Attribute definitions

title = text [CS]
    This attribute offers advisory information about the element for which it is set.

Unlike the TITLE element, which provides information about an entire document and may only appear once, the title attribute may annotate any number of elements. Please consult an element's definition to verify that it supports this attribute.

Values of the title attribute may be rendered by user agents in a variety of ways. For instance, visual browsers frequently display the title as a "tool tip" (a short message that appears when the pointing device pauses over an object). Audio user agents may speak the title information in a similar context. For example, setting the attribute on a link allows user agents (visual and non-visual) to tell users about the nature of the linked resource:

...some text...
Here's a photo of

   me scuba diving last summer

...some more text...

The title attribute has an additional role when used with the LINK element to designate an external style sheet. Please consult the section on links and style sheets for details.

MSN messenger - - doesn't give a tooltip in FF2.