Possible Duplicate:
Visual Studio - Prevent stopping debugging from closing Internet Explorer
When I start debugging my web application in Visual Studio 2008, a new Internet Explorer window opens. When I finish debugging, that new window, along with all previously-open IE windows, will be closed.
I'm tired of losing all open websites whenever I debug my app. Please, help me to find a solution!
Whenever you "run" a web app from visual studio it will, as you say start an instance of a web browser (how else will you use your application?) If you dont want this to happen you would be best to set your application up within IIS, then when you want to debug build, start a web browser, browse to localhost/App then within Visual Studio manually attach the process to the web browser instance. That way when you stop debugging the browser will stick around.
I don't know about the grammar, but I assume you want to attach to an existing IE session instead of creating a new one when debugging. Also, instead of stopping debugging, you want to Detach the IE app from the debugger.
Look in your Debug properties to see the 'Attach' debug setting.
In the project options, go to the web section. There are a bunch of start actions you can choose from. If you don't want a web browser to open, select "Don't open a page. Wait for a request from an external application". Then you can use any instance of a web browser to hit your application and it won't be tied to your debugging session.
If you're running with the built in web server, you can see the port being used by clicking the "web" icon in the system tray.