error creating a basic page
saadlulu is right - this is a notice (not an error) provided by the core node module and relates to the preview functionality you have enabled. Are you trying to disable preview?

If you just want to disable the message, try the 'disable messages' module and make sure to heed the advice here and use the following wildcard:

The trimmed version of your post shows what your post looks like when promoted to the main page.*