In SharePoint deployments, it is fairly common to have a requirement to override these pages with custom pages. You would want to do this when you want to hide fields from a user, or when you want to enhance the appearance of the page for the user.
One example of where I needed to do this is on a custom list where I had configured a SharePoint Designer workflow. The workflow was fairly complex and I had configured some extra fields on the custom list to facilitate the workflow. I didn't want the users to see these extra fields when they were creating, editing, or viewing items in the list so I had to hide these fields.
Here are the steps to configuring custom NewForm.aspx on an existing custom list. These steps may also be used to configure custom EditForm.aspx or DispForm.aspx.
* SharePoint Designer > File > Open Site
* Expand the lists folder
* Expand the custom list that you are modifying
* Double click NewForm.aspx to open it
* File > Save As
* Name the custom list something unique (do not overwrite the default NewForm.aspx) e.g.
* You will see a generic SharePoint control in the center of the page with column 1, column 2, column 3
* Right click the SharePoint control that is in the center of the NewFormCustom.aspx page, Cut to remove it from the pageInsert > SharePoint Controls > Custom List Form
* Right click within the Custom List Form SharePoint control to invoke the menu.
* Modify the Custom List Form SharePoint control.
* File, Save
* Right click the custom list container > Properties
* List Properties > Supporting Files Tab > Configure this tab accordingly, pointing NewItemForm to NewFormCustom.aspx
* Apply, OK
* File, Save
If you need the revert back to the original NewForm.aspx, you can open the list properties from SharePoint Designer, navigate to the Supporting Files tab, and point the NewItemForm property back to NewForm.aspx. Furthermore, if the requirements change, the original NewForm.aspx is still in tact and you have the option to create additional, custom NewForm.aspx pages.
Words of caution about working with the NewForm.aspx, EditForm.aspx, and DispForm.aspx:
* Always create a web part template of the custom list or document library as a backup, before making changes
* If the custom list or document library has workflow, take the additional step of creating a site template or backup the site collection entirely using stsadm
* Never rename the default NewForm.aspx, EditForm.aspx, or DispForm.aspx pages. This will corrupt the custom list. When you click on Edit Item you will receive an error, "Invalid URL." Instead use the steps above.
* After switching to the custom form, attachments are no longer supported on the custom list. If you try to add an attachment you will get an error, "This form was customized not working with attachment."
Microsoft published a knowledge base article addressing the attachment issue:
Microsoft KB 953271:
Error message when you try to attach a file in a custom form on the Web site in Windows SharePoint Services 3.0: “This form was customized not working with attachment"