The CHANGE-THIS should be changed to your flickr's NID or your flickr friendly Url i.e. whatever you see in the address bar of your flickr photostream for e.g. if your flickr photo url is http://www.flickr.com/photos/xyz you should replace CHANGE-THIS to xyz. Do keep in mind that this bookmarklet will replace whatever is there in the description field with just a link to “OnBlack” version with the text “VIew On Black”. Also, I have only tried this on Firefox and it works in almost all the scenarios that I tried.