Let's see here what we have here...
Okay that one has some science behind it...
2. Eat a healthy diet... Although making healthy selections at the grocery store and at mealtime can't guarantee cancer prevention, it might help reduce your risk.
3. Maintain a healthy weight and be physically active... Maintaining a healthy weight might lower the risk of various types of cancer
4. Protect yourself from the sun
Apparently they didn't get the news that apparently sunscreen doesn't help
For HepB sure, for HPV, the jury is still out as "Most infections with high-risk HPVs do not cause cancer. Many HPV infections go away on their own within 1 to 2 years. However, infections that last for many years increase a person’s risk of developing cancer..."
6. Avoid risky behaviors...
Like unprotected sex and sharing intravenous needles? Cancer is only a minor reason not do partake in these activities....
7. Get regular medical care...
Actual screening for cancer has only been clinically shown to be effective for breast, lung, colon and cervical cancer. This doesn't actually prevent cancer, only increased the odds of catching it before it becomes serious.
For some people, they tend to strongly advocate these things because it is what they do anyhow. As for the science behind a list like this, the science somewhat vague. Other than stopping smoking and getting your vaccinations, (one reducing environmental exposure and the HepB issue), it's a mixed bag when it comes to science.
The whole thing about eating health is that we really don't know what the hell we are talking about yet. First it's low fat, then it's low sugar, then eating cholesterol is bad, then we find out there's only a minimal relationship to the cholesterol we eat, and then we find out that there's good and bad cholesterol and then it doesn't really show a strong correlation.... Then vitamins good, then vitamins bad... Exercise good, too much exercise bad...
Of course, the answer is not to eat cheeseburgers and not exercise, the take away is to don't take all this crap on the internet as gospel, and all things in moderation, right? ;^)