For example, in Firefox, I can RIGHT-click on a specific item on the page, choose "Inspect Element" and it will list the HTML code for the specific item on the page and it will show the various websites and code that are used by the local area of the page. Or I can click on Tools-Web Developer-Page Source to show everything on the page.
In Internet Explorer 11, click on "View" in the upper left, then choose "Source".
Basically, you have to look for the specific http item in the Source and compare it with the thousands of sites that are listed in the HOSTS file.. There are a number of ways to do that, but basically, you open the HOSTS file with a text editor and "Find" the specific website in question. It takes a while to fine the right ones.
Hope this helps
Grif