The page displaying broken may be caused by the browser not using HTTP 1.1 through Proxy connections. Some sites will display correctly even if HTTP 1.1 is not set, but some will not. To make sure the browser is using HTTP 1.1 though the proxy, please do the following.
Open Internet Options and jump to the Advanced Tab.
Scroll half way down the page until you reach HTTP 1.1 Settings.
Make sure Use HTTP 1.1 through proxy connections is selected, apply changes and refresh the page, the page will now display correctly
By default HTTP 1.1 through proxy should be enabled, to confirm this, in the address bar type about:config. Say yes to the disclaimer.
In the search field search for 1.1.
Under Preference Name you will see network.http.proxy.version, make sure the Value is 1.1, if not modify the value and set it to 1.1.
Refresh the page, the page will not display correctly