Opera CSS Extensions

Support Key: [O4]
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What Are They?
Many browser makers have been following a convention of using a dash character ("-") as a prefix for proprietary CSS properties...Opera follows this convention with a few XML-specific CSS properties created to enable some functionalities in their XML rendering of WML, mail and news. (BTW, Microsoft's Internet Explorer for Win32 doesn't adhere to this convention - they have chosen to name their proprietary properties anything they feel like, which may create compatibility problems later on.)

These proprietary properties allow replaced element images and hyperlinking behavior to be included in general XML documents. An author could use XHTML for this purpose, but for cases where that is not possible, these Opera CSS properties add this basic functionality from HTML to any XML document. (NOTE: These properties only work on non-HTML/XHTML documents.)

Should you use these proprietary CSS properties and values? Opera suggests that you should not. But, as long as you keep in mind that Opera is the only browser that can utilize these properties, hanging yourself because of possible cross-browser incompatibilities should be a choice that anyone has in their development toolbox. Of course, Opera is making things as difficult as possible for authors to use these properties: with every browser version they have changed the names of these properties every time. I attempt to list these properties here mostly for completeness sake.

The following information is mostly from Opera's documentation, quoted where directly referenced.
Proprietary Opera CSS Properties
-o-replace
Support: [O7] (See note below about the previous names for this property in older Opera versions)
Inherited: No
Allowed Values:
- None: [DEFAULT] Element is not a replaced element.
- attr([ATTRIBUTE]): Element will be replaced by the contents of the URL specified in the [ATTRIBUTE] value.
Purpose:
Primarily used to to display images in XML documents...
"This property declares the element to be replaced or not. If replaced, the attr() function is used to point to the attribute where the URI to the content can be found."
-o-set-link-source
Support: [O7] (See note below about the previous names for this property in older Opera versions)
Inherited: No
Allowed Values:
- None: [DEFAULT] Do not set a link source for this element.
- attr([ATTRIBUTE]): Use the value of the [ATTRIBUTE] attribute as the link-source
- [URL]: Use the specified URL as the link-source
- [String]: Use the specified string as the link-source
- content(): Unknown - This is from Opera's documentation, but there are no examples listed to aid in understanding this usage
Purpose:
Primarily used to set the destination URL for a hyperlink in XML documents...
"This property sets the value of the 'link' variable which can later be used to generate a link through the '-o-use-link-source' property."
-o-use-link-source
Support: [O7] (See note below about the previous names for this property in older Opera versions)
Inherited: No
Allowed Values:
- None: [DEFAULT] Do not use any link-source for this element.
- Current: Use the current '-o-set-link-source' value as the destination URL for this element.
- Next: Use the next '-o-set-link-source' value (as defined in document order?) as the destination URL for this element.
Purpose:
Primarily used to set the usable activation target for a hyperlink in XML documents...
"This property sets the element to be a source anchor and, if so, declares which value of the 'link' variable that should be used: the current or the next."
Browser Peculiarities
Boring Copyright Stuff....