I had a three-fold process to delete it:

In Chrome, go to "the three bars", otherwise known as Customize and control Google Chrome. Then,

 1) under Extensions, make sure you disable and delete Delta 
 2) under Settings, in the subsection, On startup, the third bullet is "Open a specific page or set of pages" and, beside that, click the hyperlink that says, "Set pages". Hit "X" to cancel Delta.

In your Control Panel,

 3) use the Uninstall to get rid of the software.

Good luck! :)

'''''''about:config Solution is perfect......Thanks that delta was irritating for me.'''''''

Although going to "about:config" and replacing the Delta newtab URL with "any other site" (thank you), I really wanted it to return to the 3 column - 3 row tab site. So, once the URL became replaced by that about:config line with "browser.newtab.url," I further right-clicked on that line and clicked "reset." Voila, the default Firefox 23.0.1 returned to that 3/3 default state. Nothing else was deleted or changed as I remained in Firefox - clicked the "+" tab and all was well!

(See my recent reply to VINDAVER) When I went to Uninstall before I found the solution I entered a moment ago, I, too, tried to uninstall. But my version of Windows 7, would not show a "Delta..." line! After using Malwarebytes, I got rid of most of it - but the "Delta Tab" still remained until all this "about:config" was employed.

(See my recent reply to VINDAVER) When I went to Uninstall before I found the solution I entered a moment ago, I, too, tried to uninstall. But my version of Windows 7, would not show a "Delta..." line! After using Malwarebytes, I got rid of most of it - but the "Delta Tab" still remained until all this "about:config" was employed.