iOS5 gives a better solution
call this from webViewDidFinishLoad
- (void)zoomToFit
{
if ([theWebView respondsToSelector:@selector(scrollView)])
{
UIScrollView *scrollView = [theWebView scrollView];
float zoom = theWebView.bounds.size.width / scrollView.contentSize.width;
scrollView.minimumZoomScale = zoom;
[scrollView setZoomScale:zoom animated:YES];
}
}