How to set a New Tab as the start page in Firefox and lock in my choice of web sites
You may set the New Tab page Firefox shows when opening a new tab as its start page, and you can lock in the web sites you want displayed there.
I set my browser to open a New Tab as its start page and have locked in six destinations from which to choose on my start page.
First I open Firefox and open a new tab. Then I delete any open tabs other than this New Tab. Optionally, I can also set a second tab to open to a specific web site
Next I go to Tools and Options (or Edit and Preferences in Linux) and select the General tab on the far left. Click on [Use Current Pages].
Each time I open Firefox it will open showing me the New Tab.
I can select from pages that I have already visited the six pages I want to have appearing on my New Tab every time. Supposing there are no pages locked in yet, and I don't want the site in the top left. I hit the X in its thumbnail's top right corner, it disappears and every other site thumbnail moves up and there is a new site appearing in the sixth slot. Note that if I have visited one page frequently, it may appear more than once, or be replaced by itself. If that happens, just keep deleting until the page you want shows up.
If I find a site that I want to save, then there is a thumbtack in the top left corner of the thumbnail. It is black, but if I click it it turns blue, and the thumbnail is a keeper.
This web site is in the second row, second over, but I want it to be up on the top row. Just drag and drop and the two sites exchange places. Make sure it has a blue thumbtack. The lock-down thumbtacks and delete X symbols appear in the top left and top right, respectively while the mouse is hovering over them.
It is possible to delete a saved site, and it is possible to undo the thumbtack. Simply click the X to delete or click the blue thumbtack to unlock the site and turn the thumbtack black.
You may choose to tack down a few sites and let the remainder float in and out, driven by your browsing history.
Through my use of this approach, I have instant access to my club's web site, two Webmail sites, and some other often-visited places on the Web, all in one start page.
About the only thing I really don't need there is a Google search box, for if I enter my search terms in the address bar I get the same result as if I had specifically typed in the search box.
Some add-ons, often potentially unwanted programs (PUPs), will replace the Firefox about:newtab (address of the New Tab) with eBay, Facebook, Twitter icons among others, and a different search engine. These icons may have a nicer appearance than the default Firefox New Tab, but you may also be looking at extra, unnecessary work for the computer, especially if behind the pretty icons there is a hidden agenda.
Personally, I would stay clear of these add-ons, and perform some scanning with an up-to-date antivirus and antimalware software.