I totally agree with Rami, by law the website must present an age gate, it doesn't matter if the viewer of the site is in Australia, the UK, or Saudi Arabia. The law instructs the owner of the site, and not necessarily the viewer.
Although I really disagre with this rule. I feel that such an age gate should be decided upon by the owner of the website. But I'd rather see "mature content" warnings rather than age gates. After all, it should be someones right as a human to decide if they want to subject themselves to that type of content, but in many cases the government is making the decision.
Mountain Dew, happiness in a bottle.