Is it always the same page, or same kind of page? For example, advertising??

I have some concern about your extension, SaveFrom.net Helper. To the right of your post (Question Details > More System Details), it shows version 6.57, but the official release is 6.20. That seems suspicious. Could you remove the one you have and install the official release?

You can view, disable, and often remove unwanted or unknown extensions on the Add-ons page. Either:

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

In the left column, click Extensions. Then check on the right side whether you have a Remove button for the add-on and Remove it if you can. If you can't remove it, let's see whether installing from the Add-on site replaces it.

Here's the page to install from:

https://addons.mozilla.org/firefox/addon/savefromnet-helper/

Then try exiting out of Firefox and starting it up again to see whether that makes any difference.

More generally, here is my suggested approach to finding and removing bad add-ons and other types of malware that may pop up unwanted pages. I know it seems long, but it's really not that bad.

(For Windows Vista, 7, 8, 8.1, 10; XP is somewhat different)

(1) Open the Windows Control Panel, Uninstall a Program. After the list loads, click the "Installed on" column heading to group the infections, I mean, additions, by date. This can help in smoking out undisclosed bundle items that snuck in with some software you agreed to install. Be suspicious of everything you do not recognize/remember, as malware often uses important or innocent sounding names to discourage you from removing it. Take out as much trash as possible here.

(2) Open Firefox's Add-ons page using either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons
• in the Windows "Run" dialog, type or paste
  firefox.exe "about:addons"

In the left column, click Plugins. Set nonessential and unrecognized plugins to "Never Activate".

In the left column, click Extensions. Then, if in doubt, disable (or Remove, if possible) unrecognized and unwanted extensions. All extensions are optional; troublemakers might not be obvious from their names.

Often a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Any improvement?

(3) You can search for remaining issues with the scanning/cleaning tools listed in our support article: Troubleshoot Firefox issues caused by malware. These on-demand scanners are free and take considerable time to run. If they finish quickly and especially if they require payment, you may have a serious infection. I suggest the specialized forums listed in the article in that case.

Also, your Firefox identified itself to the forum as a beta version of Firefox 44. An update is available: this article describes how to get Firefox 48.0.1 using the "About Firefox" dialog on the help menu: Update Firefox to the latest release.

If something is holding you back from upgrading to Firefox 48, please let us know so we can suggest solutions or workarounds. Version 44 is not secure; Mozilla discloses security flaws after each new release.

Sometimes Firefox reports the wrong version because that information was saved in a preferences file. If the "About Firefox" dialog (see first article link) shows Firefox 48.0.1, you may need to clear out that incorrect information. See: How to reset the default user agent on Firefox.

Actually, to install a regular release instead of updating to beta Firefox 49, you can download a full installer from the following page:

https://www.mozilla.org/en-US/firefox/all/

Scroll down to your preferred language, and for maximum plugin compatibility, choose the regular Windows release, not the 64-bit Windows release which only runs Flash and Silverlight (not Java, Adobe PDF, VLC, Google Hangouts, etc.).