Managed templates are shipped with ASA2. They will be kept up to date with every ASA2 update, so you will never have to care about layout improvements or fixes.
Everytime ASA2 is being updated, the managed tempaltes will be updated too.
Here you can see an example of the newest managed template Robust:
In ASA2’s section Templates, the managed templates are marked with the yellow Managed label.
If the managed templates meet your requirements, you can stick with them and never care about updating them over time to newer browser or HTML / CSS versions.
Refer to the subpages to learn more about every managed template: