Try accessing it using a different browser. The majority of the 'regulars', here in AB's Technology area, use Firefox in preference to Internet Explorer:
http://www.mozilla.com/firefox/
If you can view the site in Firefox, but not in IE, the problem lies somewhere with your settings for Internet Explorer.
However, if neither browser can display the site, the problem almost certainly lies with your firewall. (Your firewall settings are, in any case, far more likely to be blocking a site than IE is).
One other possibility (assuming that your work PC uses a different ISP to your home PC) is that there could be a fault with your ISP's domain name server. That's the first place your request to access any web page goes to. It converts the 'www' address of the website to it's 'real' (numeric) IP address. For example, if you type 'www.theanswerbank.co.uk', the DNS converts that into '91.186.31.12', which is AB's IP address. (Try typing that numeric IP address into your browser's address bar. It will take you to AB's home page). If the DNS can't find the true IP address of the site you require, you won't be able to access it. Find the true IP address of the site you want, here:http://www.selfseo.com/find_ip_address_of_a_website.php
Enter that IP address in your browser's address bar. If it works, you'll know that there's a DNS fault (which should be reported to your ISP).
Chris