Downvoted for unnecessary snark and the non-apology in your edit (disagreement with tone is not misunderstanding). There are gentler and better ways to express this, e.g.:
Have you had a look at Greasemonkey or Stylish?
Because you can use greasemonkey to do the same thing doesn't make this worthless, and even if this replicated what greasemonkey does exactly (which it doesn't), it might still be an interesting take on an old problem. Reinvention is a great way to learn, and not very damaging for anyone else, so why not do it now and then? As long as you're willing to admit other versions might be better than your attempt, I see nothing wrong with it.
As a good example of reinvention which actually solved a lot of real world problems, see Linux (reinventing MINIX, but eventually diverged hugely), which started thus:
I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu) for 386(486) AT clones. This has been brewing since April, and is starting to get ready. I'd like any feedback on things people like/dislike in minix, as my OS resembles it somewhat (same physical layout of the file-system (due to practical reasons) among other things).