The name of the task and the hint are obviously pointing at
[robots.txt](https://en.wikipedia.org/wiki/Robots_exclusion_standard), so let's
see what's there :

```
User-agent: *
Disallow: /c4075.html
```

Now we have a path to check : `/c4075.html`. If we open the page, we
immediately get the flag :
`picoCTF{th3_w0rld_1s_4_danger0us_pl4c3_3lli0t_c4075}`