I have copied the my old site files and moving those into new site. i have changed the url in db, and uploaded the files in new server. everything works fine except the media show black images .can any one suggest me what is wrong with this.
Plugins such as Search and Replace can help you to properly fix the URLs in your database.
Likewise, consider using backup-and-migration plugins such as BackupBuddy (paid) or Duplicator (free) to properly and more easily move your site (while automatically handling the above search-and-replace operation).