To view what website's different elements are comprised of, you can use a browser's element inspection tool. Each browser has different processes of launching this tool, so let's go through all of them:
Google Chrome
Just right-click on any website's area and choose Inspect. You can also use your keyboard shortcut - Ctrl+Shift+I.
If you want to see the error log, you can select the Console tab and detect, for example, mixed content warnings:
Firefox
Again, right-click a blank area on the page or choose an element, and choose Inspect Element. Also, you can use your keyboard shortcut's - Ctrl+Shift+Q or Ctrl+Shift+C.
Opera
Use the keyboard shortcut Ctrl+Shift+I or select Inspect Element from the menu by right-clicking any element of the page.
Internet Explorer
Once more, right-click on the page and select Inspect Element or press F12 on the keyboard.