You can try these steps in case of issues with web pages:

You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• Hold down the Shift key and left-click the Reload button
• Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• Press "Command + Shift + R" (Mac)

Clear the cache and cookies only from websites that cause problems.

"Clear the Cache":

• Firefox/Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

• Firefox/Tools > Options > Privacy > "Use custom settings for history" > Cookies: "Show Cookies"

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Are all the problem sites secure sites, in other words, the address bar shows HTTPS at the beginning?

Have you see any error pages claiming that websites certificates are not valid and created any exceptions?

For Yahoo! mail, in case Yahoo has assigned you to a different server as part of its rolling upgrades, try accessing mail through the Yahoo home page and if that works, update your bookmark/home page to match the new server.

By the way, some users have reported that the Epson E-Web Print extension is not fully compatible with the updated user interface in Firefox 29-30. You may want to disable it if it isn't critical to your use of the internet.

Open the Add-ons page using either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Extensions. Then you can find E-Web Print on the right side and click Disable.