You mean Sign In or Create an Account, Social Security ? I can get there OK and it's not my government.
Check your browser settings and add-ons.
What is your operating system and service pack (if applicable)? Also what is your browser and version? Could you check to see what version of Internet Explorer is installed, whether or not you use it please?
Also see the Web Accessibility Problems section at the lower right here: http://www.socialsecurity.gov/accessibility/
You could also phone them at 1-800-772-1213 and ask them about the problem as they may be familiar with it.
My guess is however, that it's your browser. Try another one.