Important note for Firefox 12+ users
Starting with Firefox 12, Tabmix default for Events/New Tabs > "Load on new tabs" and Events/Tab Closing > "When I close last tab replace it with" options changed to New Tab Page. When you update Firefox to v.12, it resets Tabmix option to New Tab Page and you have to make your selection again. You have a few options if you had the Blank Page option selected previously:

• re-set Tabmix to load Blank Page.
• use the New Tab Page for new tabs.
• use the New Tab Page but disable it by clicking on the button on the upper right corner, this will turn the New Tab Page into blank page for new tabs.
  (or setting browser.newtabpage.enabled to false)
• set Tabmix to load the New Tab Page and set the address to about:blank.