HTML5 Parsing in IE10 (via the IEBlog) – an interesting and reassuring read!

The Web is better when developers can use the same markup and same code
across different browsers with the same results. The second
platform preview of IE10
makes progress in this area by fully supporting the
HTML5 parsing algorithm.

This continues work we started in previous releases to improve
IE’s HTML parser
to make more HTML “just work” in the same way across
browsers. Some key examples include supporting SVG-in-HTML, supporting HTML5
semantic elements, preserving the structure of unknown elements, and improving
whitespace handling. As a result of this work, most HTML parses the same across
IE9 and other browsers.

Getting the right behavior

The goal of this work is to ensure all HTML parses the same
across modern browsers. This is possible because HTML5 is the first version of
HTML to fully define HTML parsing rules, down to the last edge case and error
condition. Even if your markup is invalid, HTML5 still defines how to parse it
and IE10 follows these rules. The examples below illustrate some cases fixed as
part of these improvements.

HTML DOM ( HTML5 + IE10 ) DOM ( IE9 )
<b>1<i>2</b> |-
   |- “1”
   |- <i>
     |- “2”
   |- “1”
   |- <i>
|- <i>
< object>
  < p>Test 2
< /object>
   |- “Test 1n”
|- <object>
“n  “
   |- <p>
“Test 2n”
   |- “Test 1n”
|- <object>
“n  “
|- <p>
   |- “Test 2n”

Interoperable innerHTML

These improvements apply to innerHTML too. Code patterns like these now work
as you’d expect in IE10:

select = document.createElement(“select”);

= “<option>one</option><option>two</option>”;

table = document.createElement(“table”);

= “<tr><td>one</td><td>two</td></tr>”;

Better error reporting for developers

HTML5 ensures markup will parse consistently. It’s still a good idea for
developers to avoid writing invalid markup to begin with. Writing valid markup
helps your site work the way you expect and is more compatible with older

To help developers with this, IE10 now reports HTML parsing errors via the F12
developer tools

Screen shot of the F12 Developer Tools showing an HTML5 parsing error

Removing legacy features

Because some features in earlier versions of IE aren’t compatible with HTML5
parsing, we’ve removed them from IE10 mode. Sites that rely on these legacy
features will still work when running in legacy modes. This way, sites that work
today will continue to work with IE10 even if the developers of the site don’t
have the time to update them.



This content is ignored in IE10 and other browsers.

In older versions of IE it renders as part of the page.


This means conditional comments can still be used, but will only target
older versions of IE. If you need to distinguish between more recent browsers,
feature detection instead



<?import namespace=”my” implementation=””>


This parses as an unknown element in IE10 and other browsers.

In older versions of IE it binds to “”.



Data Islands


This parses as <b>HTML</b> in IE10 and other browsers.

In older versions of IE it parses as XML.


Your feedback welcome

We welcome your feedback making sure that all HTML parses
consistently across browsers (including via innerHTML). Download
the second platform preview of IE10
, use it, and please report any bugs you
find via Connect.

About TechPreacher

Software Development Engineer working for Microsoft in Switzerland. Focusing on the Internet of Things and Windows development. EV geek and passionate gamer, with a life.
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