Using IFrame to check if a NVR is online or not

I have a group of around 10 NVRs that I would like to be able to display on one page whether they are online or not.

Currently I do this with a HTML page containing 10 iframes each trying to load the default page of the NVR via their IPs, this either displays the default menu or just has a white error page.

Is it possible to interrogate what is in the iframe and display a green page if the connection is made and red page if not? or even to do away with the iframe and check if the IP of the NVR is live or not and display this as a visual list.