Do not use "
in url. Your link element format should be like;
<a href="http://www.domain.com?a=john" target="_blank">User</a>
You can refer here for html link format, and you can use this;
<a href="http://facebook.com/share.php?u=<?php urlencode(the_permalink()); ?>&t=<?php urlencode(the_title()); ?>" target="_blank"><i class="icon-facebook"></i><?php _e('Facebook', 'domain'); ?></a>