In order to figure out data: URL processing requirements I have been studying MIME types (also known as media types) lately. I thought I would share some examples that yield different results across user agents, mostly to demonstrate that even simple things are far from interoperable:
text/html;charset =gbk
text/html;charset='gbk'
text/html;charset="gbk"x
text/html(;charset=gbk
text/html;charset=gbk(
text/html;charset="gbk
text/html;charset=gbk"
These are the relatively simple issues to deal with, though it would have been nice if they had been sorted by now. The MIME type parsing issue also looks at parsing for the Content-Type header, which is even messier, with different requirements for its request and response variants.