Weird computer display issue

VNemeth

I have been modifying my new smugmug site using the code I have learned on this forum. The code has worked great and I am very happy with how my site is shaping up. The problem is that the changes I have made are not present on all other computers. I have made my homepage slideshow have rounded corners with a drop shadow. I also made all the folders, galleries and photos have rounded corners. When I went to work today these changes were not present when viewing my site on the pc computers there. These computers do show some of the other changes I have made with the css code.I have an ipad and a iphone which do show the changes. I have a MAC laptop that does not show the changes. I asked a couple of my friends one sees the changes and one does not on their pc computers.
My site www.vnemeth.com

Any ideas what may be the issue?
Thanks

Vic