Copying and pasting something does not necessarily mean the user will get what they think they are getting. With a little bit of HTML magic, one can even trick unwitting web site visitors into executing shell commands without their knowledge. The trick is by no means new, but it is currently being demonstrated again on several web sites which means Linux users especially have to be careful what they copy and paste
http://www.h-online.com/open/news/item/Old-tricks-are-new-again-Dangerous-copy-paste-1842898.html