07-10-2013 15:46 - edited 07-10-2013 15:48
Welcome to the Nokia Support Discussions!
The default browser of Lumia 720 is Internet Explorer. This feature is fixed. However, you can still check on the Store for other available browser apps that you can download. One example is Nokia Xpress browser.
If you are referring to the search engine, you can change it by going to Settings and flick to applications. Tap on Internet Explorer and select advanced settings. Scroll down to see Default search provider option. You can select either Google or Bing.
Hope this helps.