Saurabh_2.0 said

having problem with automatic change of default web browser

I think you are talking about the default search engine. Some add-ons or other installed programs can change the setting.

Is it changing to Yahoo?

Type about:addons<enter> in the address bar to open your Add-ons Manager. Hot key; <Control>(Mac=<Command>)<Shift> A)

In the Add-ons Manager, on the left, select Extensions. Remove Yahoo Anything. Now do the same in the computers Programs Folder.

Windows: Start > Control Panel > Uninstall Programs. Mac: Open the "Applications" folder. Linux: Check your user manual.

After the problem is fixed, Bookmark and use this; Download the Mozilla Search Reset {web link} This add-on is very simple: on installation, it backs up and then resets your search preferences and home page to their default values, and then uninstalls itself. This affects the search bar, URL bar searches, and the home page.

https://support.mozilla.org/en-US/kb/change-your-default-search-settings-firefox

Saurabh_2.0 said

Hello there i am having problem with automatic change of default web browser form google or others to firefox recommended yahoo.Which is not favourable to me. first of all tell me if this is possible to have any default search engine or not ?If yes then how?

Firefox itself is a web browser as Google and Yahoo in this case are search engines. Google has not been the global default search engine since Firefox 33.0 Release as Yahoo became the default search engine in en-US Firefox starting 34.0

Saurabh_2.0 said

Hello there i am having problem with automatic change of default web browser,s search engine form google or others to firefox recommended yahoo.Which is not favourable to me. first of all tell me if this is possible to have any default search engine or not ?If yes then how?

Yaah actually it's my fault i am talking about search engine not browser. And i don't have any add-ons exe installed in.I have tried reinstalling the browser thrice. I am having this problem in firefox only ,not in any other. Please let me know if it is really recommended by mozilla,and is it possible to change or not,if yes then what should i do?

In the searchbox right next to the magnifying glass (on the URL line) there is a dropdown menu. Can you select Google there? Alternatively, in Menu /Options /Search you can add search engines.

https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save

Note: Some software, like Advanced SystemCare with Surfing Protection, can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.