Ignore "Attribute Unavailable"-Warning in Xcode4

I'm using a lot of "custom identifiers" for Toolbar Items, which is fine in Xcode4, but it gives me a bunch of warnings when I build the project:

Attribute Unavailable Custom Identifiers in Interface Builder versions prior to 3.2

Is there a way to ignore these warnings in Xcode4? It's pretty messy when I search for "real" warnings and errors.

Click on your xib file. On the properties you will see the following section:

Where it says "Development" change that to Interface Builder 3.2 and you should no longer receive those warnings.

UPDATE for current iOS Xcode users: In iOS 4.3 - IB is built into the IDE, and on the right after selecting the xib file there will be some icons, the first icon is called "File Inspector" (looks like a page with a fold in it) that is where the section resides (see below).

I am running Xcode 4.2 build 4C199.

1. Click on xib file,
2. on the right, click on Utilies View

3. Click File Inspector. As tony.stack mentioned look under "interface BuilderDocument"
   set Deployment = "Project SDK version"
   set Development = " xcode 4.2"

   Even if you are running xcode 4.2, the Development is set to default 4.1, So you get that warning.

Have you tried looking at the "Document Info" window in Interface Builder? You can set supported versions there.