Q: Failed to load page missing Safari

Remove all that useless "anti-virus" software according to the developer's instructions.

That's very odd. Did you try with just Sophos installed, or only with both AVG and Sophos? The free version of Sophos does not include any kind of link scanner or other browser plug-ins that would cause such issues. It's very odd that this is happening with multiple anti-virus programs to begin with, but if it's happening with something like Sophos that shouldn't change browser behavior, there's likely to be a problem of some kind elsewhere.

Regarding the need for anti-virus software... for the most part, the average Mac user doesn't need any. Mac OS X protects against all currently-known malware. However, you're in China, and that changes things a bit. Certain groups in China have been heavily targeted by malware in the last couple years, and even if you're not part of one of those groups, you could still become "collateral damage." Because of the increased exposure you may have, it's probably a good idea to have some kind of anti-virus software installed as an additional layer of security. I'm sure some folks would disagree, saying that if some malware can slip past the built-in defenses in Mac OS X, it will slip past anti-virus software as well. That's not a universal truth, though... different detection methods can have different levels of success for specific malware. The holes in one layer of defense may (or may not) be covered by a different layer.

For more information about this sort of stuff, see my Mac Malware Guide.

You can avoid malware by enabling Gatekeeper on your Mac.

Open System Preferences > Security & Privacy then select the General tab.

Make sure either Mac App Store or Mac App Store and identified developers is selected. If that area is grayed out, click the padlock icon to proceed.

OS X: About Gatekeeper

Avoid Avast, Norton, MacKeeper........   they will only cause problems for you.

You should try downloading google chrome its quick and it refreshes the current tab rather than all so it keeps your laptop quick and clean!

Maybe you could consider backing up your whole macbook and restoring the whole system for a clean start. There may be some sort of bug or application that is causing your mac to do that. Just an idea you could consider! May be alittle struggle but its worth it!

i download a lot of unrecognised applications because i like to customise my mac

That's more likely to be the cause of your problem than any anti-virus software you've got running. You've probably got a bunch of junk software installed that hacks your system, resulting in all manner of potential problems.

You don't need to reinstall Safari. You need to get rid of the "anti-virus" software.

Reinstalling Safari isn't going to do you any good. The Safari app isn't the problem.

Honestly, as I've already said, I think it's very weird that you've gotten the same problem with two different anti-virus apps. When such apps block access to a site, that's not the way it should happen, and the fact that you had the same odd behavior with both suggests to me that there's something else wrong. I think it wouldn't be a bad idea to just erase the hard drive and resintall a fresh system. (See How to reinstall Mac OS X from scratch.)