Description of problem:
nav header is hidden when I scroll the page

Version-Release number of selected component (if applicable):
* candlepin-0.8.25-1.el6sam.noarch
* candlepin-scl-1-5.el6_4.noarch
* candlepin-scl-quartz-2.1.5-5.el6_4.noarch
* candlepin-scl-rhino-1.7R3-1.el6_4.noarch
* candlepin-scl-runtime-1-5.el6_4.noarch
* candlepin-selinux-0.8.25-1.el6sam.noarch
* candlepin-tomcat6-0.8.25-1.el6sam.noarch
* elasticsearch-0.19.9-8.el6sat.noarch
* katello-candlepin-cert-key-pair-1.0-1.noarch
* katello-certs-tools-1.4.2-2.el6sat.noarch
* katello-cli-1.4.3-10.el6sat.noarch
* katello-cli-common-1.4.3-10.el6sat.noarch
* katello-common-1.4.3-12.el6sam_splice.noarch
* katello-configure-1.4.4-4.el6sat.noarch
* katello-glue-candlepin-1.4.3-12.el6sam_splice.noarch
* katello-glue-elasticsearch-1.4.3-12.el6sam_splice.noarch
* katello-headpin-1.4.3-12.el6sam_splice.noarch
* katello-headpin-all-1.4.3-12.el6sam_splice.noarch
* katello-selinux-1.4.4-2.el6sat.noarch
* thumbslug-0.0.34-1.el6sam.noarch
* thumbslug-selinux-0.0.34-1.el6sam.noarch


How reproducible:
Always (in Firefox 17.0.7)

Steps to Reproduce:
1. Navigate to SAM 1.3 UI -> Dashboard
2. Use Down Arrow key to scroll down to the end of the page


Actual results:
1. Notice that the nav header is hidden (Screenshot 1)
2. When I mouse over, the nav header comes back, but the nav header menu items are not highlighted when mouse over (Screenshot 2)

Expected results:
1. The nav header should not disappear when scrolling down
2. Mouse over on the nav header menu items should highlight the items

Additional info:
1. Happens all the time in Firefox 17.0.7
2. Works fine in Chrome 26.0.1410.63