I'm looking forward to know how they do this. They update their information on just a couple of ms and I see no AJAX requests on my firebug console.
Here is the page: Económico
As you can see on this two images below, this is the information they are updating.
Thanks for your help, looking forward to extend my knowledge!
They are making requests using websockets
e.g.
Request URL:ws://ortc-prd2-useast1-s0002.realtime.co/broadcast/444/m38tirp9/websocket
Request Method:GET
The responses are in Frames
So not your usual stuff, what firebug are you using? It is likely not reported in the console, but in the Network tab.