Q: MacKeeper

Hi!

So I surfed online and then I saw the "you have a virus on your mac" message and I've downloaded the MacKeeper that he told me to download for free to delete the virus. Luckily when I was trying to install the software, it kept failing on the last level, telling me to approach my software manager or something. I deleted the installation and emptied the trash. I can't tell there is something different on my Mac but I'm still worried. Should I do something to make sure I don't have any "leftovers" from this software/virus?