From B2evolution

[edit] Completing installation

Once your installation is done and basically working, there are still a few tricky things you should definitely take care of:

• When you edit any of the config files, be careful not to add any extra blank lines at the start or end of the file. For some very tricky reasons, this will cause your cookies to fail where needed in the app, and you won't know why.
  See also FAQ#"Cannot modify header information".

• In the /blogs folder there is a file called [ sample.htaccess ]. You should try renaming this to [ .htaccess ] . This will optimize the way b2evolution is handled by the Apache webserver. This file is not active by default because a few hosts would display an error right away when you try to use it. If this happens to you when you rename the file, just remove it and you'll be fine.

• If you get any file permission errors when running b2evolution, then you must take care of changing all necessary Directory and file permissions.

[edit] Completing upgrade

If you are upgrading from an older version of b2evolution, be sure to follow on to the upgrading page and check if there are specific instructions for your specific upgrade path.