First, there is a white line after the first div and another before its closing. It gets messy when there is hundreds of them. i.e. it's hard to find a footnote. I suggest removing these white lines.
Second, there is no space inserted after the tag, so instead of seeing "[1] Lorem ...", I get "[1]Lorem". This could be fixed by CSS, but using :after is not, AFAIK, supported by all current ebook readers.
I have two issues with the way the footnotes are generated: