I agreee with Monika it is the align to pixel option and you must have it turned on.

If you are making a web document it is turned on my default

the transform panel reflects this unless you do not have the options of the transform panel opened.

here it shows it

Here it doesn't

Here witht the option I choose .5 pixels in the stroke panel

The result is 1 pixel

This is the only way this situation manifest itself.

On the web you cannot have less than a pixel.

Otherwise you must have something installed on your system that is drastically effecting AI CS 6.

But I am certain that Monika is correct.

Nice one!

Rodieck you are missing the point if you have align to pixel option turned on then it will not be possible to assign a weight of less than a pixel because of the nature of align to pixel.

So if youwant to assign less than pixel you hsave toturn thr option off before the weight field will allow it.

So she made a mistake we all do! No?

You can also simply open the web rgb document turn it off and replace it then it will always be that way.

You find the document profiles here you need to right click or control click on the Illustrator Application and choose Show Packages.

You make the changes then resave the file by doing a save. I am not certain if it is possible to do a Save As to the packages so do a simple save.

They're are in the required folder.

If you ever wish to do a custom arrow head or 3D extrusion profile they are also located in thye Packages.

It actually feels more like a bug then a poor implemented feature to me...

I'm using CS6 for a week now, and I use it to create "technical drawings" (Illustrator just works for everything right) that can be cut using a laser cutter; something totally different then web design, which relies on pixels and rasterisation processes.

I found that even in a Print/CMYK document the strokes of the rectangles would not go below the 1 pt, and immediately jump back. According to my reasoning, this has nothing to do with any of the pixel grid align functions, since I am working in a document with millimeters as the standard measure and pt to define stroke size. In CS5 I did not have these problems and I could easily set the stroke to the desired size < 1pt.

So my thought is: maybe it's an actual bug, these pixel grid options should be ignord when working with print intention right?

.... I agree, I've noticed I can have two objects with "align to pixel" off and the appropriate global settting has been turned off; then, when I do a boolean operation suddenly the new object has "align to pixel" on and all the anchor points get skewed. ...

This happens when you have the "Align New Objects To Pixel Grid" checked in the menu of the Transform panel accessible from the top right corner of the panel.