First, open the browsers’ developer tools:

– Chrome/Firefox: Press ++I (on a Mac) or F12 (on Windows).
– Alternate: Right-click anywhere on the page. In the context menu choose “View Page Source”.

Then, search the page source:

– Open the “Elements” tab of the developer tools
– Now hit +F (Mac) or Ctrl+F (Windows) to search for anything, like a tag, attribute or string