Steps:
1. After login to the server where the CVS repository is stored, go to the folder of the project:
cd [project_folder_path]
2. Delete the wrong revisions from CVS, for a specific file:
cvs admin -o [file_revision_number]: [file_folder_path/file_name]
The command "-o [file_revision_number]:" deletes all the file's revisions, starting from the specified number, including the respective revision and all the way to the end of the branch containing the respective revision.
Example:
cd /home/projects/myWebsite
cvs admin -o 1.10: public_html/calendar/availabilityView.jsp
Useful resources:
http://cvsman.com/cvs-1.12.12/cvs_133.php