I thought it'd be a nice idea to include my del.icio.us tagrolls on my homepage. This is made possible by some JavaScript served up by their website. Unfortunately their implementation relies on document.writeln() which is not compatible with XHTML.
Undeterred, I created imposter versions of document.write and document.writeln. My implementations progressively concatenate the parameters into a buffer. When the web page loads, the buffered XHTML is positioned appropriately by using an empty placeholder tag.
I originally tried parsing the buffer as an XML document, with the intention of merging the XML nodes into the XHTML document. I tried using xmlDoc.documentElement.cloneNode(true) as a parameter for appendChild() on an XHTML node.
While this worked like a charm in both Firefox and Opera, Internet Explorer complains of "Interface not supported" and Safari has a fatal error! The failing browsers have an incompatibility of XML and XHTML DOM nodes, even though they both support a common DOM interface.
In the end I had to write my own version of cloneNode() to copy elements between the incompatible schemas and ensure valid nesting of elements. There's an exception handler that fails over to using innerHTML complete with IE kludges just in case.
If you're interested to see how this was achieved, please feel free to view the JavaScript source code.