If you found this online (vs a .pdf, .jpg, etc):
Using Google Chrome as your browser: you can can go back to that site, select the font and right click select "Inspect Element". It will bring up an area through which you can see the css and therefore the font that the designer/developer used (unless they hid it, then searching through the 5 fonts suggested would be easier/faster).
AKA: find site using Google Chrome: select text in the font that you want --> right click --> select "Inspect Element" --> scroll through the CSS on the right hand side for "font-family"
Using any other browser: right click --> select "View Page Source" --> select the .css file --> find "font-family"