To expand on keshlam's answer:
A direct feed does not involve a website of any kind. Each exchange publishes its order/trade feed(s) onto a packet network where subscribers have machines listening and reacting.
Let's call the moment when a trade occurs inside an exchange's matching engine "
T0". An exchange then publishes the specifics of that trade as above, and the moment when that information is first available to subscribers is
T1. In some cases,
T1 - T0 is a few microseconds; in other (notorious) cases, it can be as much as 100 milliseconds (100,000x longer).
Because it's expensive for a subscriber to run a machine on each exchange's network -- and also because it requires a team of engineers devoted to understanding each exchange's individual publication protocols -- it seems unlikely that Google pays for direct access. Instead Google most likely pays another company who is a subscriber on each exchange around the world (let's say Reuters) to forward their incoming information to Google. Reuters then charges Google and other customers according to how fast the customer wants the forwarded information. Reuters has to parse the info it gets at
T1, check it for errors, and translate it into a format that Google (and other customers) can understand. Let's say they finish all that work and put their new packets on the internet at time
Then the slow crawl across the internet begins. Some 5-100 milliseconds later your website of choice gets its pre-processed data at time
T3. Even though it's preprocessed, your favorite website has to unpack the data, store it in some sort of database, and push it onto their website at time
A sophisticated website might then force a refresh of your browser at time
T4 to show you the new information. But this forced refresh involves yet another slow crawl across the internet from where your website is based to your home computer, competing with your neighbor's 24/7 Netflix stream, etc. Then your browser (with its 83 plugins and banner ads everywhere) has to refresh, and you finally see the update at
So, a thousand factors come into play, but even assuming that Google is doing the most expensive and labor-intensive thing it can and that all the networks between you and Google and the exchange are as short as they can be, you're not going to hear about a trade -- even a massive, market-moving trade -- for anywhere from 500 milliseconds to 5 seconds after
T0. And in a more realistic world that time will be 10-30 seconds.
This is what Google calls "Realtime" on that disclaimer page, because they feel they're getting that info to you as fast as they possibly can (for free).
Meanwhile, the computers that actually subscribe to an exchange heard about the trade way back at time
T1 and acted on that information in a few microseconds. That's almost certainly before
T2 and definitely way way before
T3. The market for a particular instrument could change direction 5 times before Google even shows the first trade.
So if you want true realtime access, you must subscribe to the exchange feed or, as keshlam suggests, sign up with a broker that provides its own optimized market feeds to you.
(Note: This is not an endorsement of trading through brokers.)