closing internet browser (google) without having to use task manager all the time

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http://forums.androidcentral.com – my mate has updated his Samsung Galaxy SII to 4.1.2 as his phone was slowing down and internet wasn't working well. But now there's a problem when it comes to exiting the internet as when he thinks he has he later finds out on task manager that its still running which isn't good cause that will make the battery go flat quicker. we've had a look on the internet gone through the lot and been on websites but were still not getting answer based on this phone and how to exit the browser properly without using task manager to end it :) might seem silly but it would be nice if someone on here knows h (HowTos)