The easiest way to run a web page that's already in your browser after you've made changes to the code for the page is to

click on the Reload or Refresh button

Explanation:

If you are having problems with a page that loads slowly or does not display correctly, you can refresh the page. Depending on which Internet browser you are using - Internet Explorer, Firefox or Chrome - the buttons may be in different areas of the screen or look slightly different. However, it does not matter if they are different since each button will give the same result: the web page you are viewing will reload or update.