If you are having issues with accessing any CAC enabled (Government) sites please follow the below steps:

Open a new Internet Explorer Browser.

Select Tools then Internet Options.

On the General Tab: Select the "Delete..." button under Browsing History.
This will open the "Delete Browsing History" window.
Check Mark all boxes except for "History", then select Delete.
The "Delete Browsing History" window will close.

Select the "Settings" button under Browsing History.
Select the "View files" button which will open a separate window to your "Temporary Internet Files" folder.
Select (CTRL + A) and Delete (Shift + Delete) all of the files in your "Temporary Internet File" folder.
Close the "Temporary Internet File" folder window.
Select "OK" to close the "Temporary Internet Files and History Settings" window.

On the Content Tab: Select the "Clear SSL State" button.
When prompted with the "SSL Cache Cleared Successfully" window, select OK.

On the Advanced Tab: Select the "Restore advanced settings" button.
Select "Apply" then "OK", which will close the Internet Options window.

Close your Internet Browser.
Open a new Internet Browser.
Go to the CAC enabled (Government) website that you were having issues with.

Some CAC enabled (Government) websites (GCSS, MCEITS, etc) require slight setting changes.
After completing the above steps you should make any site specific changes. You may have to adjust you settings as you go between websites.

Marine Corps Training and Education Command