From the help file:
To position static text or groups of elements
1. On the Layout menu, click Insert Layer. Visual Web Developer inserts a div element with positioning information set.
2. To move the div element, click the selection symbol, and then drag it to a new position.
3. To resize the div element, click the selection symbol, and then drag the resize handles.
4. To add text, click inside the div element, and then type the text.
5. To add elements, drag them from the Toolbox to the div element.
Basically what they've done is remove the 'Grid Layout' and replaced it with a div tag that you place absolutely. Then the tags you place with in it will be flow.
Alternatively you can just skip all of that and once you drag the control on the page, right click, hit style, and then on Postioning choose Offset from normal (relative) or absolute position.
I don't know why they've done this. I'm sure there is a reason, but thankfully I extremely rarely use Grid Layout, so it's not a problem for me. Sorry that you have to deal with it. If you find a reason why, let the rest of us know!