Just so you know, the sample CSS given for footnotes (http://flagrantdisregard.com/footnotes-plugin/) contains a mistake. This line :
.footnotes li {
should read :
.footnotes ol li {
Also, it's not clearly written where the sample CSS is to be put. It should put in the file "style.css" of your theme folder.
I write these remarks, so that future users don't struggle like me.