I have a contribute user who has modified the layout of one of the pages, and added an XML webpart. Logged in with my SysAdmin account, I do not see his changes. It appears only for his account. I'm not sure how this is possible. It's not a mysite or anything, it's one of the main pages of the site. My contribute users usually only add/remove documents from Doc Libs. Can anyone tell me how this user is able to do this? Thanks!

Click the Welcome menu at the top of the page, click "Personalize this Page". These customizations are private to that one user. After doing this they would then select Welcome menu, "Show Shared View". After the page has been personalized they can then select Welcome menu, "Show Personal View". You can prevent this by customizing permissions. Mike Smith TechTrainingNotes.blogspot.com

Domo arigato Mike Smith!