It's got nothing to do with the tab control. You haven't added a webbrowser control to the new tab so it's not surprising that telling the non-existent control to navigate results in an error. As you've chosen the least helpful way to give us a view of your problem I'm not able to say exactly how you should go about correcting it in specific terms but the gist of it is simply add a new control to each tab page as it's created. Nothing comes of nothing!