Body text may contain markup. The markup is XML-based, and consists of a small subset of HTML along with a few additional tags.
The following tags should be supported by the notification server. Though it is optional, it is recommended. Notification servers that do not support these tags should filter them out.
A full-blown HTML implementation is not required of this spec, and notifications should never take advantage of tags that are not listed above. As notifications are not a substitute for web browsers or complex dialogs, advanced layout is not necessary, and may in fact limit the number of systems that notification services can run on, due to memory usage and screen space. Such examples are PDAs, certain cell phones, and slow PCs or laptops with little memory.
For the same reason, a full XML or XHTML implementation using XSLT or CSS stylesheets is not part of this specification. Information that must be presented in a more complex form should use an application-specific dialog, a web browser, or some other display mechanism.
The tags specified above mark up the content in a way that allows them to be stripped out on some implementations without impacting the actual content.
Hyperlinks allow for linking one or more words to a URI. There is no requirement to allow for images to be linked, and it is highly suggested that implementations do not allow this, as there is no clean-looking, standard visual indicator for a hyperlinked image.
Hyperlinked text should appear in the standard blue underline format.
Hyperlinks cannot function as a replacement for actions. They are used to link to local directories or remote sites using standard URI schemes.
Implementations are not required to support hyperlinks.
Images may be placed in the notification, but this should be done with caution. The image should never exceed 200x100, but this should be thought of as a maximum size. Images should always have alternative text provided through the alt="..." attribute.
Image data cannot be embedded in the message itself. Images referenced must always be local files.
Implementations are not required to support images.