When testing, using http://msdn.microsoft.com/en-us/library/994c0zb1(v=vs.110).a... as the target URL, I selected an item in the table in the "Remarks" section of the page and the resulting URL was "undefined/?url=http%3A%2F%2Fmsdn.microsoft.com%2Fen-us%2Flibrary%2F994c0zb1(v%3Dvs.110).aspx&top=1442.4700012207031".

I'm using IE11 on Win7.

I've built something similar, though I've used a different approach: http://tldr.es