The website appears to be coming back for most people. More than likely if it is still down for you, it should be up relatively shortly. It is probably just an issue with delayed DNS caching.
Someone believed to be from Bank of America released the following statement on twitter, “We are diligently working to fix the issue and our teams are fully engaged to have the website up and running as soon as possible.”
The website has been down for over 3 hours for some banking clients, but many are now able to access the site. There has been a lot of downtime with other banking websites as of late. Usually the cause is nothing serious, and they are back up and running pretty quickly.
