These are just tools that make some common operations a little bit more convenient. They save time and clicks.
Does Zynga allow it?
This is what Mafia Wars’ Terms of Service says:
“If you cheat on any of our games, use any hacking scripting or editing programs in Mafia Wars, violate the Mafia Wars rules or break the law, we can freeze or terminate your account, or if appropriate, report you to the police.”
Hacking refers to the re-configuring or re-programming of a system to function in ways not facilitated by the owner, administrator, or designer. Bookmarklets used under no circumstances maybe counted as hacking or an editing program, rather it is just a utility which helps you by reducing your clicks in the game and making it more interesting.
How to install a Bookmarklet?
Install the bookmarklets you want by dragging them to your bookmarks toolbar. (If you’re using Internet Explorer, dragging doesn’t seem to work. Instead, right-click on the link and then choose “Add to favorites”. For Chrome and Firefox users just drag them to your bookmarks toolbar as told earlier)