To disable a login message, go into Login Message Management and click the red cross icon next to the message you want to disable.

To edit a login message, click the cog icon next to the message you want to edit.

You can edit the contents of a login message including the acknowledgement frequency.
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Each time a user acknowledges a login message, there's a log entry created.
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To clear these logs, select Yes next to the Clear Logs radio boxes, and click Modify Login Page.