Once your web site is online modifying it takes some thought as people may have book marked particular pages. File and folder names are part of a page's url and will be what search engines and bookmarks store.
Your site users will be annoyed if you have deleted pages or moved them to other folders and they get a 404 message which tells them the page cannot be found.
Before you make changes to folders, galleries or locations of files, keep a copy of the old version(s).
Deleting or re-naming folders:
Try not to do this. If you do, be certain you want to as visitors who have book marked pages will not be able to find the old pages. It is best to leave them in place, even if the pages are changed to only show a message linking your visitor to the new location.
Deleting or moving pages/files:
Consider leaving pages you no longer want in place but delete the content (perhaps leaving the heading) and replace it with a friendly message and a link back to your home page or other suitable place. You can monitor whether the old pages are visited in your host's statistics reports and delete the pages when they no longer get visitors.
Modifying pages
Modifying individual pages/files by updating the contents is fine as long as you do not move their location/folder.
Changing Titles
This is fine. Improving a title is a good thing.
page updated 27/5/10