Mobile web site development - images and device orientation?

I have developed a mobile site with a 320px wide image on the page. When viewed on the iPhone in portrait orientation, all is. But when you view in landscape mode, it obviously doesn't fit the page. How to fix so that the image will fit all devices, regardless of orientation?

You can change Css codes. Just use the below code in default section of your stylesheet.
img { max-width: 100%; height: auto}