Some of the websites are showing up in codes?

From the menu bar, select

 ▹ System Preferences... ▹ Network ▹ Advanced... ▹ DNS

Under DNS Servers you should have one or more numerical addresses, such as “192.168.1.1” or “10.0.0.1”. What are those addresses?

Please read this whole message and be sure you understand all of it before doing anything. Back up all data before making changes to your settings.

Click Cancel to close the Advanced sheet. Unlock the preference pane, if necessary, by clicking the lock icon in the lower left corner and entering your password. Open the DNS tab again and change the server addresses to the following:

8.8.8.8

8.8.4.4

That's Google DNS. Click OK, then Apply.

In Safari, select

Safari ▹ Preferences... ▹ Privacy ▹ Remove All Website Data

and confirm. If you’re using another browser, empty the cache. Test. Any difference?

Notes:

1. If you lose Internet access after making the above change to your network settings, delete the Google servers in the Network preference pane, then select the TCP/IP tab and click Renew DHCP Lease. That should restore the original DNS settings; otherwise restore them yourself.

2. I’m not advocating Google or anything else as a DNS provider; the server addresses are offerred merely for testing purposes. There may be privacy and technical issues involved in using that service, which you should investigate personally before you decide whether to keep the settings. Other public DNS services exist.

Revert the changes to the network settings.

From the Safari menu bar, select

Safari ▹ Preferences ▹ Extensions

If any extensions are installed, disable them and test. If there's no change, re-enable the extensions, then in the preferences dialog select

Privacy ▹ Remove All Website Data

and confirm. Test again.

And after removing website data?

Please read this whole message before doing anything.

Disconnect all wired peripherals except those needed for the test, and remove all aftermarket expansion cards. Boot in safe mode* and log in to the account with the problem. The instructions provided by Apple are as follows:

1. The process by which OS X checks the validity of root SSL certificates doesn't work behind the authenticating SOCKS proxies used on some enterprise networks. If applicable, contact your network administrator. The proxy server may need to have its settings changed.

2. Disable the built-in application firewall and any third-party firewall, "security" software, or network filter. Failing to do this is a common mistake. Test.

3. In some versions of OS X, Parental Controls has a bug that prevents loading of secure websites. Turn it off.

4. Are the current date (including the year) and time shown on your system clock? If not, correct them and test.

5. Launch the Activity Monitor application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Activity Monitor in the icon grid.

Select All Processes from the menu in the toolbar of the Activity Monitor window, if not already selected. Enter "ocspd" (without the quotes) in the "Filter" text field. Is a process with that name listed?

If not, select

Go ▹ Go to Folder

from the Finder menu bar. Into the text box that opens, copy the following line of text:

/var/db/crls

From the folder that opens, move these two files to the Trash:

• crlcache.db
• ocspcache.db

You’ll be prompted for your administrator password. Reboot, empty the Trash, and test.