First, thanks for sharing this plugin ;)
Running a validator on my site, I notice a little "bug" (validator was right at this time ;) ) in
include/wpsr-socialbuttons.php, line 357, where params needs a space (at least in my case)
//'params' => 'class="wp-socializer-single"', need space before class 'params' => ' class="wp-socializer-single"',
or somethink else somewhere else... I didn't go through the code...
Without it, this source is generated for mail:
</div><div class="wpsr_floatbt"><a href="mailto:?subject=... title="Email this" target="_blank" rel="nofollow"class="wp-socializer-single">
where a space is missing between rel="nofollow" and class
May be also needed for other cases. Doing this, I didn't notice any other problem (was no problem before as well... but;)).