• The certificate for the source may not be authenticated You can only add certificates to your list of trusted sources if they have been authenticated (authenticate: Process used to validate a certificate's source delivered by a Web site or used to sign a macro. If the security level enabled on the computer cannot authenticate the digital signature, the certificate is ignored or the user is prompted.).

  Note  Certificates created with the Selfcert.exe tool are considered to be unauthenticated and can only be added to the list of trusted sources on the computer on which they were created.

• The list of trusted sources might be locked Your system administrator might have locked your list of trusted sources so that you cannot add new macro developers to it.

• The macro might not be digitally signed In order to add a macro developer to the list of trusted sources, the macro must be digitally signed (digital signature: An electronic, encryption-based, secure stamp of authentication on a macro or document. This signature confirms that the macro or document originated from the signer and has not been altered.) by the developer.

• You might not have Internet Explorer 4.0 or later installed on your computer Microsoft Internet Explorer version 4.0 or later is required in order to digitally sign a macro or verify that a developer is trusted.

• The security level might be set to Low In order to add a macro developer to the list of trusted sources, you must change the security level to Medium or High.

If you use Microsoft Internet Explorer version 4.0 or later, the Certificate Properties dialog box appears when you click the Details button in the Security Warning dialog box. The Trust tab in the Certificate Properties dialog box provides an option to trust the certificate; however, Microsoft Office 2003 programs will ignore any options you set on the Trust tab. Use the Security Warning dialog box to add a macro developer to the list of trusted sources.

Digital certificates (digital certificate: Attachment for a file, macro project, or e-mail message that vouches for authenticity, provides secure encryption, or supplies a verifiable signature. To digitally sign macro projects, you must install a digital certification.) created with the Selfcert.exe tool are considered unauthenticated (authenticate: Process used to validate a certificate's source delivered by a Web site or used to sign a macro. If the security level enabled on the computer cannot authenticate the digital signature, the certificate is ignored or the user is prompted.). Microsoft Office 2003 will allow you to add the owner of an unauthenticated certificate to the list of trusted sources only when the certificate is used on the same computer on which it was initially created. This means you can run Selfcert.exe and create a certificate on your computer, sign your own personal macros, and you can trust that certificate on that same computer. However, if you attempt to share the file with another user, the other user will be unable to run the macros if his or her security setting is set to High.