1) goto Control Panel » Display Options -Tab- HTML Includes
enter what you want in Default Header:
when posting html code just use what is between the body tags.
2)Probably is a code modification, Currently I am not sure what to edit since each one would be a different url. It might be easier to just place the link in the forum introduction
Control Panel » Forum Settings » Edit Forum -tab- Custom inserts
3)Could be, but probably was a hickup with your connection to your host while the changes were submitted and the data got hosed.
