Hello, to make ICQ your default Browser type "Default Programs" in the search bar of your OS and then click on "Set Default Program" here you can search your ICQ browser and make it default by clicking the given button below.

if you still face difficulty, feel free to reply

Firefox, Chrome, IE, et al. are web browsers.

http://search.icq.com/ is a web based search engine. And you can get a ICQ search engine for Firefox from the Mycroft Project. http://mycroftproject.com/ It will install to the Search Bar in Firefox, and can be set as the default search engine as explained here: https://support.mozilla.org/en-US/kb/use-search-bar-firefox-and-manage-search-engines