If you do Web Application development, you've no doubt struggled with the task of creating Modal forms.  You have different options for doing this, each with their own advantages and pitfalls.  Hosting your form in a new browser instance (window.open()) is really a kludge, and many users have popup blocking software which will break this approach. Using true Modal dialogs (window.showModalDialog()) doesn't work well from within ASP.NET.   Using draggable DIV elements solves some of these issues, but has its own set of problems.  Dragging DIV elements involves using DHTML and JavaScript and the script that you have to write to enable this can be tricky.  Toss browsers other than IE into the mix, and you've got even more problems.

Taking all this into account, I've come up with an approach that works pretty well from within ASP.NET applications.  Sticky Draggable Divs! (SDDs) ;)  They involve using DHTML Behaviors, and .htc files. If you're not familiar with this technology, see http://msdn.microsoft.com/library/default.asp?url=/workshop/components/htc/reference/htcref.asp. 

So, check out my example of SDDs.  I've included the source files in a .zip file here.

Creating SDD's is easy! Just follow these steps: 

1. Create an ABSOLUTELY positionable DIV element
2. Reference the DragParent.htc file
3. Include the DragParent namespace in the page's HTML element.  
4. Wrap an element within <DragParent:DragParentDiv> tags

Any element included within the <DragParent:DragParentDiv> tags will become the anchor to enable dragging of that element's parent DIV control.  Within the .htc file, events are attached to the element to support the dragging.  When the dragging is complete, a cookie is set so that the element will be positioned properly for postbacks. This is also done automatically for you by the .htc file.

For this to work well, and for the windows to be Draggable, your users have to be using Internet Explorer 5 or above.  I can count on most of my users to be using IE.  Mozilla users won't be able to drag the window, but this is okay since they can still see the content.  The best part is that these nerds won't get JavaScript errors, because Mozilla won't parse the HTC script. 

-Brendan