It occurs to me that it would be a useful convention for any script that creates and adds elements to the document to tag those elements by adding "synthetic" to the class attribute of the element
This way, other scripts that run later can identify elements that were not part of the original document. Some scripts will want to process syntehtic elements along with the originals, but some will want to skip those synthetic elements.
I don't have a compelling example use case to argue for this, but it just seems like as we start writing more and more useful unobtrusive scripts, we'll find that they interact with each other in unexpected ways. I haven't written any greasemonkey scripts myself, but I suspect that a convention like this would be helpful there, too...
Could someone please post a short example of a script that adds elements to the document dynamically.
There is one problem with adding clutter (in a way, anything you don't have a specific purpose in mind for, is) like this is that not all browsers handle any number of class names gracefully.
Specifically IE5 and 6 (IIRC) will only apply CSS styles for the two first class names given. I expect the "synthetic" class name would typically always be the last name appended, though, so in practice this probably isn't a very real concern.