You can check the browser.newtab.url pref on the about:config page and set that pref to your preferred new tab page.

• the default new tab page with the tiles is about:newtab
• the default home page is about:home
• for a blank page you can use about:blank

The browser.newtabpage.enabled pref should be set to true to use the page set via browser.newtab.url as the new tab page.

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

You can use the SearchReset extension to reset some preferences to the default values.

• https://addons.mozilla.org/firefox/addon/searchreset/

Note that the SearchReset extension only runs once and then uninstalls automatically, so it won't show on the "Firefox > Add-ons" page (about:addons).

You can check for recently installed suspicious or unknown extensions.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Sounds suspicious. Here's my suggested procedure for tracking down and cleaning up bad add-ons, which are a common cause of new tab page hijacking. I know it seems long, but it's not that bad.

(A) Open the Windows Control Panel, Uninstall a Program. After the list loads, click the "Installed on" column heading to group the infections, I mean, additions, by date. This can help in smoking out undisclosed bundle items that snuck in with some software you agreed to install. Be suspicious of everything you do not recognize/remember, as malware often uses important or innocent sounding names to discourage you from removing it. Take out as much trash as possible here.

(B) Open Firefox's Add-ons page using either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons
• in the Windows "Run" dialog, type or paste
  firefox.exe "about:addons"

In the left column, click Plugins. Set nonessential and unrecognized plugins to "Never Activate".

In the left column, click Extensions. Then, if in doubt, disable (or Remove, if possible) unrecognized and unwanted extensions.

Often a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Any improvement?

(C) You can search for remaining issues with the scanning/cleaning tools listed in our support article: Troubleshoot Firefox issues caused by malware. These on-demand scanners are free and take considerable time to run. If they finish quickly and especially if they require payment, you may have a serious infection. I suggest the specialized forums listed in the article in that case.

Success?

I tried using about:config and set the values to about:blank but it keeps popping up with fast start. I'm sorry to ask again.

See this - http://malwaretips.com/blogs/quick-start-new-tab-page-removal/

You need to get rid of the program that installed that "Fast Start" garbage. If you don't, it may get re-installed in your web browsers. Be aware that the name of that malicious program may be different than what MalwareTips mentions. So, get rid of anything that you don't specifically need or remember installing.