It's a diet designed to boost immune function and prevent HPV from becoming cervical cancer. It sounds like something that would be only marginally successful, though a strong immune system has lots of other benefits. It's a far better idea to simply get the HPV vaccine, thus preventing infection altogether.
A diet will not decrease your chances of HPV infection. HPV is a sexually transmitted virus that can only be avoided by abstinence or using protection (not affective in all cases). If you are concerned you may have or may get HPV, seek the advice of a health care provider.
The HPV diet is a diet full of veggies and fruits, herbal and botanical supplements, as well as drinking green tea. It is only in my opinion that this diet does work, but would probably work for most any type of disease that you're trying to prevent.
Foods that contain nutrients which may help your body heal - leafy greens, oranges, red peppers, papaya, carrots, and pumpkin are examples. All are good for you and can't hurt.