We cannot help you unless you help us to know about your computer, The thing is firefox can crash for millions of reasons, First thing you need to do is to file a crash report as soon as it gets crashed. If you want help from here, Tell us about your OS, Firefox Version, Addons Installed, It is high chance there might be a problem with your installation, try uninstalling and re installing the latest version from https://www.mozilla.org/en-US/firefox/new/ You may also seek help from : https://support.mozilla.org/en-US/kb/firefox-crashes-troubleshoot-prevent-and-get-help