Fixed selection/outline rect issues when layout.css.devPixelsPerPx was non-default, also fixed the floating element count being outside of upper document bounds, changed the test page a bit.
Fixes #22, Fixes #23
Please give the latest beta a try: https://github.com/cpriest/SnapLinksPlus/raw/master/dist/snaplinksplus-2.3.4b8.xpi it should have this problem solved.