Information Gift

XML vs. AOL

Ran into an interesting compatibility issue this week with XHTML documents and the Classic (pre-OS X) version of Mac AOL 5. Hitting index pages with this combination unexpectedly causes AOL to present your page as a download instead of simply rendering the page.

It appears that the problem is caused by adding an XML declaration before the XHTML DTD. This just happens to be the default behavior of both BBEdit and Dreamweaver MX, and I would expect newer versions of other commonly used editors to also follow in this behavior. After all, one of the drivers of using XHTML in the first place is to allow for easy interoperability with XML user agents and tools; if you are valid XHTML, then you can also be valid XML with the declaration.

The fix:
If Classic Mac AOL users are part of your intended audience, and XML compatibility is not a must-have, then the fix is to simply drop the XML declaration. This will allow your pages to still validate as XHTML and render, but will no longer validate or interoperate with XML tools.

Note that Classic Mac AOL 5.0 for OS 8.1 - 9.x uses Internet Explorer 4.01 as its browser. I would expect, but have not tested, that the stand-alone version of IE 4.01 would also fail with this scenario. AOL for OS X users are not affected by this problem.