Quality of images in UIWebView for iPhone4

I'm using UIWebView to display some content in my view. It works fine, except for the quality of images in it (when running on iPhone 4). I link those to the resource bundle from HTML using the following code:

 NSBundle* mainBundle = [NSBundle mainBundle];
 NSString *strAbsBundlePath = [[mainBundle resourceURL] absoluteString]; 
 NSString* strImgFileName = @"some_image.png";
 NSString* imgTag = [NSString stringWithFormat:@"", strAbsBundlePath, strImgFileName];

As always I include two versions of the same image into the bundle:
some_image.png --- 32x32
some_image@2x.png --- 64x64

But the approach above simply makes images larger on the screen (which I don't need, because it messes up the HTML formatting) instead of improving the quality.

Is there any way to fix that?