Assuming that the web browser is compatible with modern web standards...

1. Get an account with a web-based electronic stock trading platform, for example, E*Trade or TD Ameritrade.




2. Use your 5 seconds insight to buy low and sell high.




3. Enjoy your filthy lucre.

Iterate.

Set up a webcam pointed at your computer screen with the browser open, use another computer to watch the webcam through another instance of the browser, set up another webcam and another computer with another instance of the browser.....

Each additional computer that you add to the chain will give you a further 5 seconds insight into the future.

With 60 camera/computer/browsers in a chain, you have five minutes insight into the future - easily enough to place bets on races, poker, games of chance. You'll even be able to see when suspicion is aroused about your activities sufficiently in advance to avert it.

The more money you make, the easier it'll be for you to create an even bigger machine with more layers and more "foresight" - you should then be able to see what oilfields yeald fresh reserves, where archaeological finds yeald hords of gold jewels, artifacts (and get there first, at your leisure) you'd see future technology (and the technical plans/specs on Wikipedia or future equivalent) and be able to invent it first. You could save the world by discovering the secrets of cold fusion. Find out what's in Dr Pepper.

You'd be able to find the secret of immortality (at least long life and cell repair) and graft any convenient physical and mental abilities onto yourself. You' could create a high-tech self-repairing army to protect you and do your bidding.

You'd see what political strategies would lead you to become the president/primeminister/premiere of your chosen country - then what strategies would lead to your becoming ruler of the world.

You'd discover timetravel - go back to just after when the browser was created, kill the creators.

So, to sum up.:

• You rule the world.




• You own it.




• You're immortal.




• You can predict your enemies strategies before they were even born.




• The worlds resources are at your disposal to do with as you will - to expand off planet, or to parallel worlds (if such exist - you'd know).




• No living person can do what you do and noone knows how you did it - you have no serious rivals and no peers.




• You now know exactly what happened on the grassy knoll on that fatefull day and what's up with area 51.

Scalping

Ticket scalping is the process of buying additional tickets to resell at a profit for events. Most of these events use a platform like Ticketmaster.com and the sale only starts on a specific day and time.

Using your browser you can go to the release of a highly desired event and purchase a number of valuable tickets. Since these high profile shows sell out within days if not hours your 5 second lead time should help purchase the tickets before legitimate users. Afterwards you can resell on things like Facebook market place.

ebay

You can start ebay reselling. It is easy enough to discover the true value of a product with some googling. Make a list of the really good deals and then shortly after a product closes bidding you have 5 seconds to place the lowest possible winning bid.

After the purchase you put it back up on the internet with a better value so you can profit from the difference.

Just sell it.

In speed trading seconds are highly valuable. To a company engaged in that the fair market value of your browser would have to be tens if not hundreds of millions. Full five minutes of advance time on competition would be pretty much license to print money. You would have to figure out a way to filter out the effects of your own trades on the accuracy of the prediction but those guys could pull it off.

Does the browser have magic prophecy powers, or just your specific installation? Because the first would mean that it's unique, and others have given pretty good answers about how you could use that.

If you can just download it to any and as many machines as you want, you end up in a vastly different universe, and I'd like to go open up that angle a bit, because I think you need to either consider this or come up with a very good reason as to why it's not used by everyone. This thing will spread, because it's far too useful, too interesting, and too good of an opportunity to make money for it to stay secret for very long.

In that scenario, it's only a matter of time until many, most, and all other people use it and have the same advantage, resulting in nobody having a real advantage anymore, but being forced to use this browser. Race betting etc. would break down, because nobody would offer these bets if they know that betters know the winner. In stock trading, you'd end up in a similar state to reality, where people fight about microseconds again after everyone has that 5 second advantage.

I'd go so far as to say that in this scenario, you actually could not make much money with this, unless you are one of the early adopters, or you get very, very creative. I could imagine scammers using this in some convoluted "bet on a coin toss while secretly glancing at the browser that shows me a webcam image of the result" scheme, but other than that there's not much room for getting rich quick. Except for one: you have control over the browser's functionality somehow, and can charge people for using it - provided nobody can reverse engineer it and create an open source version or something.