This was working prior to FF41
Someone said to install New Tab Override to make this add on work properly in FF41, however unless I'm missing something, that add on simply replaces this one and gives no ability to open a new tab to the current web page which is the appeal of newtaburl for me.
The behavior I'm getting in FF41 is, having installed NewTabToolbarbutton, when I click that button I get a new tab opened to the current page which is what I have newtaburl set to do. When I type Ctrl-T, I get this list of suggested webpages or having installed NewTabOverride and entered about:home in it's options, I get a webpage opened to google which isn't my home page.
Maybe if there was readily accessible documentation about what those newtab options in about:config do we could have some chance of making this work. I'm pretty sick of firefox breaking stuff constantly.
Isn't there a code for "current webpage" that we can put in New Tab override?