https://jupiter.challenges.picoctf.org/problem/9670/
After inspecting the website, it was found that the first part of the flag was in one of the comment of the HTML source code.
<!-- Html is neat. Anyways have 1/3 of the flag: picoCTF{tru3_d3 -->
The second part of the flag was in the CSS file named mycss.css.
/* You need CSS to make pretty pages. Here's part 2/3 of the flag: t3ct1ve_0r_ju5t */
Also, it can be seen that there is a comment in the myjs.js file the contains the 3rd part of the flag.
/* Javascript sure is neat. Anyways part 3/3 of the flag: _lucky?2e7b23e3} */
Combining all the parts of the flag, the flag is:
picoCTF{tru3_d3t3ct1ve_0r_ju5t_lucky?2e7b23e3}