How to Use HTML5 Now to Create a Website

Can I use HTML5 Now to create a website

I built a site in 100% semantic HTML5, tested only in Firefox, Chrome and Safari. When I was done, I added these three scripts and loaded it up in IE6 and IE7 - ~~looked pixel-perfect!~~ ok, perfect is an exaggeration. It doesn't look exactly the same, but it looks fine e.g. no broken layout parts, everything is legible and functional.

HTML5 Shiv script - Add HTML5 element support
ExplorerCanvas - Add <canvas> support
IE PNG Fix (IE6 only) - Add transparent PNG support

YMMV but these will almost certainly get you at least 90% of the way.

Use of HTML5 for a new website

Thank god MS is finally campaigning to get gid of IE6 but it surely will be in China for years to come due to pirated windows software which I had altogether too much experience with; despite this push for higher standards tons still use IE7, 8, and some even 9 is not perfect. Chrome IMOP is exceptional followed by Safari and FF for HTML5 support but even these browsers are not perfect.

I think it is ok to use features css3 and HTML5 such as canvas but in an unobtrusive manner like javascript enhances UI HTML5/CSS3/jQuery should enhance not be the content.

With javascript we can check for browsers and use appropriate methods this concept should also be applied to HTML5. So if you do implement anything I think it's important to understand how to detect and this is probably the best resource to start with.

http://diveintohtml5.ep.io/detect.html

How to create a desktop only website using html5-boilerplate?

I have found an easiest possible solution to this and its working for me. I just added following code into CSS file (my media query section of at bottom of main.css in case html boilerplate).

@media only screen and (max-width: 900px) {
    /* Style adjustments for non responsive websites */
    body{width:940px;}
}

Should I code my website in HTML5 in 2013?

I suggest you give "The truth about html5" a read if you have the time.

Html5 so to speak offers a lot of new stuff. But the reality of the market is a bunch of stuff either just plain works with a handful of browsers, and other stuff has been around for years and simply got included under the so to say html5 branding.

Also keep in mind that ie8 still represents a huge piece of the pie of the ie landscape and will do so for years to come. In the end it all comes down to what your project target audience is and how many percent of users you are willing to sacrifice or allowed to sacrifice.

Caniuse.com should be of good use to you, and understanding when and how too use polyfills too.

Myself I manage a big site which uses a bunch of html5, css3, and responsive design that scales from mobile phones to tablets to desktops, and works just fine in ie7 too.

But it didn't suffice to say hey let's code it in html5, but instead took a lot of reflection and compromises to get there.

So actually my answer would be: use the parts of css3 that degrade gracefully as much as you like. The parts of html5 that you find indispensable ..at the condition you have a fallback polyfill in place. And the rest ..think 20 times before jumping on the buzzword bandwagon.

In the end you don't even have to choose between html4/5 or css2/3. You can mix and match both easily .. as the latter simply build on the previous. As long as you know what you are doing, and why.

But yes learn it !

Is valid HTML5 OK to use now?

I'd recommend checking out Dive Into HTML 5 and deciding for yourself if you think the tradeoffs are acceptable. So far as I've heard, there are no negative SEO implications for using HTML 5. I just ran the w3c validator on Dive Into HTML 5 and it automatically detected that it was HTML 5 and validated it, so I don't think that will be a concern, either.

Advice and considerations for converting HTML4 to HTML5 website.

You don't have to use GIMP to design everything from scratch, follow the steps described here:

http://www.w3schools.com/Html/html5_migration.asp

they will guide you to convert your existing website to use HTML 5

Do HTML5 development using grunt and bower with WebSite project or create HTML5 Web app in Visual Studio 2015?

When developing a template, my research so far shows that:

Patience, grasshopper, it's early days. ASP.NET Core 1.0 just released, but does not include certain elements, including a new .xproj style set of projects for basic pure HTML 5 web project development (name not yet even announced, but let's hypothesize, it might be called Core Pages), whatever it is, the Microsoft "franchise reboot" for Pure HTML5 Development with Microsoft Visual studio either doesn't exist yet, or is in early stages of internal development. Whatever template I could make today might be obsolete in three weeks or three months if Microsoft makes a move here.
For now, for people who can live with it, File -> New Web sites works fine, and I haven't found any technical documented reason why you CAN'T use it for new development, just a caution from Microsoft that it might not be the best choice, if a File -> New Project template can meet your needs. You can see from the way that ASP.NET Core 1.0 today works (just in time automatic-recompile without rebuilding in ASP.NET Core brings a core feature of the WebSite world over into the WebApp world at last) that its new tooling and the new .NET Core features inside dnx and dnvm will finally "restore the Balance of Nature" that I feel has now been divided over the last 10 years by the WebSite/WebApp dichotomy. Not yet, but that's part of the core design elements I have understood from studying the ASP.NET Core architecture.
For ExtJS, the Sencha Ext JS plugin for Visual Studio provides a File -> New Web Site option, and this works fine. I downloaded and tested it yesterday evening and it works fine. If I want to invoke grunt or bower, or bundle and minify, or any other web-dev workflow task, I can do so manually using an external command prompt window as well. So while it might not be as shiny as I was looking for, it's possible to get work done. The Ext JS plugin provides full Ext class hierarchy code-completion, and starter templates for both pure HTML5 (via file New Website) and HTML5+ASP.NET (via File New Project). When evaluating their plugin I initially thought there was NO way to do a pure HTML5 app inside visual studio because I was totally unaware of the File New Website option, and thought (incorrectly) of this area of VS as deprecated.
For Angular SPA development INCLUDING .NET there is this template, and it appears you could use it and just not write any ASP.NET server side stuff if you wanted to do a pure HTML5 SPA.
I would probably suggest starting with the angular SP development template linked above and modifying it to subtract angular and insert ExtJS, or using the ASP.NET 4.6 plus ExtJS template provided by Sencha's IDE plugin, and just subtracting all the ASP.NET code from that template. I don't yet have a starter template suggestion for the ASP.NET Core 1.0 .xproj world yet.
It should be possible, and seems quite easy to use .NET Core and ASP.NET Core as a key part of the tooling for a pure HTML5 development environment. In particular "dnx web" is a useful way of locally developing, as it is even more lightweight than using IIS Express. It should be equally feasible to develop for HTML5 with "DNX web" (kestrel) as the lightweight static server for pure HTML5, and either a full Visual Studio 2015 project (either website or webapp), or using just a modern web-editor like Visual Studio Code.

I hope that other developers who are still confused, as I was about the now-10-years-long split-personality issue in visual Studio with regards to New Web Site and New Web Application, may finally see some light at the end of the tunnel.

Update: Q4/2016: It actually looks like the two way split personality issues in VS 2015 will get worse in VS 2016 (Currently in preview as VS15) because there will be THREE ways to open a project, open solution/csproj via one menu item, open web project via another, and open folder via a third.