VS 2003 - Alters .aspx files when opening

Hi,

Does anybody know why immediately after opening .aspx files from a project,
VS 2003 alters them? The alteration isn't visible in the file but an
asterisk on the file tab appears (indicating a change) and our source
control provider (Vault) notices the alteration and prompts us to check out
the file, which is a slight pain in situations where we only want to view
the file.

Any help is appreciated.

Regards,

Duncan Eley
Application Developer