Why does HTML 5 promise to be one of the coolest things ever?

The new emerging standard for coding websites essentially moves your browser closer in nature to an operating system and allows designers and developers to explore native, interactive features without resorting to plug-ins to achieve the same affect.
In tandem with CSS3 and JavaScript, creative designers can explore new graphics libraries like WebGL which offers some innovative 3D features.
HTML 5 also means we are moving away from the terms static (and even dynamic) towards something else more powerful: Applications.
For instance check out this awesome Virtual Tour or 360-degree effect offered up by Apple for an iPod Touch.
In combination with JavaScript and CSS3, the native web app allows you to rotate the image simply by clicking upon it. This was created entirely with web standard technologies and delivers a rich-media experience.  Visit the Safari Developer Library to grab some of the code examples, including the CSS Effects Photo Gallery.
Of course, Apple slants its demos towards the Safari web browser, but MOST of their examples should work on other browsers, too, including Firefox.

Here is another great example of visual photo transitions pulled off using HTML 5 web standards.
Dissolves, Toss, Slide-ins, Iris, Fade Throughs – all highly recognizable animations from famous Video Editing suites such as Final Cut Pro are now available natively within the HTML 5 Standard.
“CSS3 animations can also leverage hardware acceleration, so your effects will be smooth and fluid on iPad and iPhone — especially when compared to animations created with older, conventional JavaScript animation techniques,” said Apple.
Since the iPad has become the most iconic visual pieces of hardware on the market, transforming the way users interact with physical features and software apps, its important to keep this product in mind when designing new websites.
In fact, there are even some studies from Adobe that suggest that iPad users are the most likely out of all Smart Device owners to make a purchase online.  This makes them a valuable target market, too.
For this reason check out this How-To guide from Apple outlining out how to prepare your content for an iPad.
Even if you don’t own an iPad for testing purposes, you can use the iPhone Simulator from Apple. iPad is available in the iPhone Simulator in iPhone OS 3.2 SDK beta 2 and later, which is available to iPhone Developer Program members.
And, remember, plug-ins are not supported in Safari on iPad, nor are they supported in Safari on iPhone. Have Fun!