To keep track, one way is to drop a comment (but later delete it so as not to confuse yourself!), but another is to use the "link photo" feature, grab the URL- the first part (the a href bit, before the greater-than sign) in the "text link" - save that in a text file if you need to... this only sounds complicated... -
then find the folder you're rating on the left (you may need to increase "idx= " if you've gone more than 100 in :) so that you're on the right _page_)
then "view source" in your browser
then in the URL you grabbed, take the number immediately following i=. just the number
and search for it twice.
That way you'll find the id number - the position in the images - if you want to know it.
(Then now that you know what number image it is, you can find the image, and "copy the link location". DO NOT USE THIS TO SAVE THE IMAGE without permission (unless it's not an image they have rights to to begin with, of course))
This takes practice and doing.