Hi,
I would suggest you to reset the Internet Explorer and Mozilla Firefox settings to default.
To reset Internet Explorer, follow the steps below:
1. Close all Internet Explorer windows that are currently open.
2. Open a new Internet Explorer window.
3. Click on Tools and then click Internet options.
4. Click the Advanced tab, and then click Reset.
Select the Delete personal settings check box if you would also like to remove browsing history, search providers, Accelerators, home pages, Tracking Protection, and ActiveX Filtering data.
5. Click Reset in the Reset Internet Explorer Settings dialog box.
6. Click Close once Internet Explorer has finished applying default settings and then click Ok.
7. Restart Internet explorer.
For resetting Mozilla Firefox settings, follow the steps below:
1. At the top of the Firefox window, click the Firefox button, go over to the Help sub-menu
and select Troubleshooting Information.
2. Click the Reset Firefox button in the upper-right corner of the Troubleshooting Information page.
3. To continue, click Reset Firefox in the confirmation window that opens.
Firefox will close and be reset. When it's done, a window will list the information that was imported. Click Finish and Firefox will open.
If the issue still persists, try to boot the system in Safe Mode with Networking. Shut down the system and once you restart keep tapping the F8 key which would take you to Advanced Boot Option screen. Using the up and down arrow key, select Safe Mode with Networking to boot the computer into Safe Mode with Networking.
Once you are in Safe Mode with Networking logon to your user profile and browse the internet.If it works, reboot system in normal mode and disable or uninstall firewall applications.
Since, the issue started 3 days back, I would also recommend you to perform System Restore. Use the link below to guide you through the steps of System Restore:
http://dell.to/SbNkFw
Glad to assist you.
Thanks and Regards
Priyanka S