If web proxy settings are not being propagated to Windows 8 systems running Internet Explorer 11, configure the proxy setting.
With the release of Windows 8 and Internet Explorer 10/11, the proxy settings were no longer managed in the usual place in the Active Directory Group Policy Object (GPO).
For a bit of background on those changes and links to more in-depth information, see this blog post, THE NEW WAY TO CONFIGURE INTERNET EXPLORER PROXY SETTINGS WITH GROUP POLICY.