This test determines if your page has a viewport meta tag in the header. The viewport meta tag lets you modify the virtual viewport applied to the page and to target those modifications to particular viewport sizes. In effect, it instructs the browser when and how to zoom a page to achieve optimal rendering. Better rending within the browser improves user experience and allows webpages to dynamically adjust to different device types.
Checking for Viewport
This test checks to see if the page header contains a viewport meta tag. It does not check the internal logic or consistency of the viewport rule. If no viewport meta tag is found in the page header then the test reports a FAIL.
If you receive a FAIL for this test, you should consider adding a viewport meta tag to your page header.
This test is based on a Google PageSpeed best practice. See https://developer.mozilla.org/en/docs/Mozilla/Mobile/Viewport_meta_tag for more details on implementing the Viewport meta tag.