IDEs launch a browser when you run the web application. You can instruct IDE to launch the browser that you would like. Your system default browser might be Chrome and you might want you're development done with Firefox because of it's simplicity to identify/debut the HTML elements and Javscript issues.
I'm going to explain how we could modify the default browser with Netbeans IDE
1. Choose "Options" from "Tools" menu. IDE will open options dialog box as displayed below
2. Choose the browser from "Web browser" drop down. All the browsers installed on your machine will appear on this drop down. The default option is "<Default system browser>".
For some reason, if IDE has got the browser path wrongly, you can modify by clicking the "Edit" button.