By default, the host is the site for any run-time designer that does not display a visual interface. However, you can override this default for designers that require siting in a different application.
By specifying the DESIGNERFEATURE_DONTSITE flag under the DesignerFeatures registry key, you can request that the host not site the designer's run-time instance, so the designer can instead be sited in another application.
For example, a designer that is hosted by Visual Basic but requires its run-time instance to run in Internet Explorer must specify DESIGNERFEATURE_DONTSITE to ensure that it can be sited in Explorer.
See Chapter 11, "Registry Reference," for details.
The designer can also set the OLEMISC_SETCLIENTSITEFIRST flag in the registry to request that the application site it before loading the instance. By default, the application sites the designer after loading.