Are you using WordPress as a Content Management System (CMS) for your website/blog? Then you need to read this post.From WordPress 2.6 there is a feature which called revisions. This feature automatically saves a draft when you starting a post and it always updates with in a pre determined intervals. You can manage the revisions by using some WordPress plugins but here we use a simple MySQL query which deletes all WordPress revisions form your database.
Go to your phpMyAdmin and run the following query, it will delete the revisions.
DELETE FROM wp_posts WHERE post_type = "revision"