Ios – Black bar appearing in UIWebview when device orientation changes

I have a UIWebView that I am loading onto another view, everthing looks fine in portrait or landscape when rotating, however when I am in portrait and I zoom in slightly with pinch or double tap when I rotate from portrait to landscape the view dosnt fill completely with the uiwebview, there are about 10pxls on the right that turn black as outlined in this screen shot.

if you look carefully you can see the outline of the scroll indicator in the black, which segests this is part of the uiwebview?? if so then why dose it turn black in this area.

Also heres another screen shot of the webview scrolled up abit so you can see its part of the uiwebview…

This is how I am adding the view onto the detail view.

- (void)viewdidload
//..

//Load in FirstView
    firstView = [[FirstMainViewController alloc] init];
    firstView.view.frame = CGRectMake(0.0, 0.0, firstView.view.bounds.size.width, firstView.view.bounds.size.height);

    firstView.view.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;

    firstView.view.backgroundColor = [UIColor whiteColor];

    [self.view insertSubview:firstView.view belowSubview:actionTabBar]; 

//..