I would like to have a div that looks like on the image attached to this thread, but I would like it to be maximum flexible, so that width and height are in %, not in px.
Any ideas how to do that?

Also, I would like to have a layout that have 3 columns, first one should be in percents and second and third in px, but second and third are NOT generated on every page, and I would like the first one to take their space also if they are not generated, so this is an example:
1)

[ div 1 ] [ div 2 ] [ div 3 ]

2)

[ div 1 ] [ div 2 ]




3)

[ div 1 ]


I hope you understand and sorry for bad English!

So something like;

<div style="position:relative;width:25%;border:1px solid #666666;padding:5px;">
<div style="position:absolute;text-align:center;width:15%;left:5%;top:-10px;background-color:#ffffff;">Text</div>
 Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.
 </div>

For Q1

and Q2
You would create a single column as a 100% wide container. Then cols 2 & 3 would be created inside the parent and floated to the right at 100% height.
This way the parent container content would flow around the other 2 if they were there and occupy full width if they are not.

The only proviso, would be to ensure that the right most columns are in the parent before the text content.

If I get time I'll do a DHTML demo of it.

Lots of 2 and 3 column layout examples can be found here:
http://css-discuss.incutio.com/?page=CssLayouts

Thanks people, I'll try this, sounds like a good solution!