After upgrading to Firefox 24, many of the users having problem as new tabs are not being opened, no matter how many times you click the + sign or hit ctrl+T. It actually opens the tabs, but you can’t see it.
This problem is mainly caused by the toolbar you are using.
Disable the ASK toolbar or Google Toolbar, and you are good to go. But unlike ASK, Google Toolbar is ancient and unsupported for a long time. People like me just can’t stop using our favorite Google Toolbar. So, what option do we have? Setting browser.newtab.preload to false in about:config fixed it for me.
Type about:config into your browser, and click I’ll be careful, I promise.
then type browser.newtab.preload into the long search bar that appears,
then set the Value to False, restart browser and it should be working fine just like it did for me.