If you use Internet Explorer as your browser (versions 7 and 8), you may need to make GoMaps a "Trusted Site" for the site to work properly.
Go to Tools/Internet Options:
Click the "Security" tab, then click on "Trusted sites":
Click the "Sites..." button, then enter "http://gisweb.hendersoncountync.org" into the text box (copy/paste or type). You may need to un-check the checkbox that says "Require server verification (https:) for all sites in this zone".
Click the "Add" button. You will see the site added to the list of trusted web sites:
Click the "Close" button to close the "Trusted sites" window. Then, hit the "OK" button again to close the "Internet Options" window and you're done.