We can use Home and Power buttons to capture the screen of your iPhone and iPad. But if you want to capture the whole webpage, the webpage capture app Mammoth Web2Pic should be able to meet your requirements.
Mammoth Web2Pic is a practical webpage capture app developed by Yichao Ji, and designed for both iPhone and iPad. The universal app features neat and intuitive user interface. When you activate the utility app, a built-in web browser will be displayed in front of you. Of course, the main objective of the app is not to provide you a navigating way for your favorite websites, but use the below camera button to capture a full-sized image of the web page which you’re browsing and save a compressed image into your camera roll, while the full-resolution image can be exported via iTunes. Apart from that, the utility app also allows you to share the image with friends via Twitter.
Mammoth Web2Pic with a size of 4.8 MB is compatible with iPhone, iPod touch and iPad running iOS 4.0 or later. The universal app is free for a limited time at present. If you’re interested, jump to App Store for more details.