Just in case you never played an online-change-the-url-riddle:

You put your answer (to go to the next level) in the (end of the) url.

Right now the url word is 'first'. Replace that word with your answer.

Never use spaces and never use capital letters.

If it's the wrong answer, you get a page with a cat.

If so, then go back (in your browser) and try a better answer.