Alzrius said:
This comes up periodically, and is something of an unresolved debate. I recommend reading the excellent article on this, stating that you do need to be of the listed caster level to make the magic item, found here:
http://home.comcast.net/~superdan.net/dndfaq2b.html
I suggest you too to read that article.
Then ask yourself: do you believe what is written in the book, or do you believe what the author of the same book says about it?
I believe the author. Monte Cook wrote the DMG, he
designed the item creation rules. He explained more than once that in his design the caster level listed for each item is
not a requirement, but admitted that the wording in the book is misleading. He complained that the misleading wording was never corrected, not even in the 3.5 reprint.
The author of the article above prefers to play in a different way, which is not at all worse. But in the articles he just argues that there is a discussion with two points of view who cannot agree, and his conclusion is that therefore the "best" way is to play is (doh!) his favourite.

It seems that D.R.Collins even twisted this Monte's phrase, in order to support the idea that the discussion is confusing enough to give no credit to Monte himself:
Monte Cook said:
"Things that should have changed, but didn’t: Caster level is still a prerequisite for magic item creation. This was an error in the 3.0 DMG and remains."
Monte here is saying that the 3.5 DMG should have corrected the misleading wording which seems to suggest that CL is a prerequisite, but unfortunately it still seems from the current wording that CL is a prerequisite indeed. He's complaining that this should not be the case.
Daniel interprets Monte's sentence as he was intending that CL should be the prerequisite, therefore he says that since even Monte contradicts himself, then the solution to the question is to read the rules as they are written. But Monte (the one in charge of deisigning the 3.0 DMG) never changed his mind at all.