Sigh, don't you people bother to check if there is another discussion on ANY topic? seriously this has been raised in at least 9 previous discussions and in every single one the same advice was given.
1. DON'T USE MARQUEE The website is not designed to handle it.
2. To remove it you must use a mobile device such as an Ipad or Ipod. a laptop or PC doesn't handle the coding.
3. Don't add stuff to your front page without checking out whether you can, some things (like Marquee and embedded music) are banned.