Set default URL for new tab in Firefox
This is further to the post on Firfox tip Set multiple pages as home in Firefox.
This tip would allow you to set a custom page whenever you open a new tab (Ctr+T).
You need to install New Tab URL add-on to achieve this.
On successful installation you will be able to
Select default URL when new tabs are opened: “Blank page”, “Home page”, “Current page” or a user defined URL.
Simple dialog box provides you various options to set a default URL for your new tab.
Download Add-ons : New Tab URL