Appendix 1: Internet Explorer 6 to Internet Explorer 9 Browser Changes

	Design Changes from Internet Explorer 6 to Internet Explorer 7	Design Changes from Internet Explorer 7 to Internet Explorer 8	Design Changes from Internet Explorer 8 to Internet Explorer 9
Internet Explorer Versioning	When a long user agent (UA) string encounters a server that accepts shorter UA string only, the user will be presented with an error page.	Internet Explorer 8 Compatibility View mode, turned on by default for intranet sites in Internet Explorer 8, actually sends an Internet Explorer 7 user agent string; to differentiate between Internet Explorer 7 and Compatibility View, look for the new Trident token.	Check for code that incorrectly creates a special case for Internet Explorer, Internet Explorer 8, or Internet Explorer 9 by using user agent (UA) string sniffing, version vectors, or conditional comments. Internet Explorer 9 sends a short UA string by default, without pre- and post-platform registry value tokens. Compatibility View mode, turned on by default for intranet sites in Internet Explorer 8, actually sends an Internet Explorer 7 user agent string; to differentiate between Internet Explorer 7 and Compatibility View in Internet Explorer 8, look for the Trident 5.0 token.

Note

Check for code that incorrectly special cases around Internet Explorer 6, Internet Explorer 7, or Internet Explorer 8 by using user-agent string sniffing, versions vectors, or conditional comments.

Quirks mode exception: As a rule of thumb, no standards compliance changes are needed for webpages that specify the Quirks mode DOCTYPE (by setting “standards-compliance” DOCTYPE switch to “off”).

	Design Changes from Internet Explorer 6 to Internet Explorer 7	Design Changes from Internet Explorer 7 to Internet Explorer 8	Design Changes from Internet Explorer 8 to Internet Explorer 9
Standards Compliance Updates Applies to specified document modes. IE8 Compatibility View mode, on by default for intranet, generally reverts standards updates from IE7 to IE8. Use the EmulateIE7 X-UA-Compatible HTTP header or META tag to enable Compatibility View mode on websites or specific pages.	Applies to Internet Explorer 7 Standards or “Strict” mode and above: XML prologs in first line of source code no longer cause DOCTYPE declarations to fail. Box model overflow content now intersects box, no longer auto-grows box div to fit content. Certain CSS filters (for example, *HTML, _underscore, and /**/ comment) are no longer supported. Only outermost OBJECT in nested objects is instantiated. Applications that relied on SELECT element to get an HWND to use with Microsoft Win32 APIs may break because SELECT element is now a windowless control. Channel Definition Format (CDF) is no longer supported, in favor of RSS feeds. XBM, an imaging format designed for X-based systems, is no longer supported. BASE tags outside of the HEAD document are no longer allowed.	Applies to Internet Explorer 8 Standards mode and above: Unclosed P elements are now automatically closed when followed by TABLE, FORM, NOFRAMES, or NOSCRIPT elements. Malformed HTML is no longer supported, in favor of well-formed, valid markup. “className” attribute syntax no longer supported, in favor of “class” syntax. The attributes collection no longer contains all possible attributes recognized by Internet Explorer. Attribute ordering has changed, affecting attributes collection, innerHTML, and outerHTML. GetElementById is case sensitive and no longer searches name attributes. Generic CSS prefix selectors (that is, v\:* syntax) no longer supported, in favor of explicit tag names. CSS expressions no longer supported, in favor of improved CSS support or DHTML logic. Code intended for custom JSON object methods may conflict with IE8’s new native JSON object. Unset properties on the currentStyle object now return their initial value. This is the root cause of issues with the ASP.NET menu control (example). Unset properties values on the style object now return empty string.	Applies to Internet Explorer 9 Standards mode and above: Internet Explorer 9 does not recognize angle brackets (<>) within the createElement method. OBJECT fallback is not included in DOM and matched by window[name]. arguments.caller property is not supported in Internet Explorer 9 standards mode. Automatic binding of binary element behaviors does not work. Calling a method with a function pointer without “.call”, or “.bind” is no longer supported. Content attributes and DOM expandos are no longer connected. APIs are not available if iFrame is removed from DOM tree. Dynamic VML patterns may not work – the VML behavior must be attached to an element before any VML properties are assigned. Thai and East Asian text and font sizing may appear smaller than other typefaces. Indirect ‘eval’ function calls behave differently. Overlapping formatting elements are cloned to reduce ambiguity in the DOM. Some behavior-connecting methods do not work in XML mode. styleSheet.title is readonly in Internet Explorer. Table object mode is now more consistent with other browsers. Text layout uses natural metrics instead of Graphics Device Interface (GDI) metrics. White spaces are preserved in the DOM. Some DOM events are deprecated in favor of more standards-compliant events. For more information about other changes, see Web Applications and Standards/Interop Improvements on these posts. Applies to all document modes in Internet Explorer 9: Array elements with large indices are handled differently. JavaScript properties may be enumerated differently from how they were enumerated in Internet Explorer 8. Math precision differs in Internet Explorer 9.

Note

For sites and applications where accessibility is a concern, be sure to update ARIA syntax across all Internet Explorer rendering modes.

Check the complete list of CSS updates from Internet Explorer 6 to Internet Explorer 8.

Internet Explorer 9 contains some assistive technology improvements, but is not fully functional with some assistive technologies. See the list of issues in the Internet Explorer 9 release notes.

	Design Changes from Internet Explorer 6 to Internet Explorer 7	Design Changes from Internet Explorer 7 to Internet Explorer 8	Design Changes from Internet Explorer 8 to Internet Explorer 9
Security Improvements Apply regardless of document mode. Security features can be turned off using Group Policy.	window.opener trick used to bypass the window.close prompt is no longer allowed. Object caching protection is enabled by default, which blocks access to references of objects when users browse to a new domain (applies to Internet Explorer 6 and later on Windows XP Service Pack 2 and later). DHTML scriptlets are now disabled by default. Scripts that write to the status bar are now blocked. URL creation may fail if URLs do not meet RFC guidelines. HTTPS pages will display an error page if site is configured to SSLv2 only, or if site security certificate is outdated, invalid, has errors, or has weak ciphers. Only “punycode” encoded internationalized domain names are supported; other formats like ANSI and UTF-8 are now blocked. Cross-domain script URLs, redirected navigation in DOM objects, and frame navigations are now blocked. Modal or modeless dialogs created from script might seem slightly bigger. Unsecure protocols view-source, Gopher (at the WinINET level), and Telnet no longer work.	XSS filter is on by default. This blocks script patterns that most frequently resemble Type-1 XSS attacks, unless disabled by site developer through X-XSS-Protection HTTP header. Cross-domain, cross-document communication hacks like SCRIPT SRC are no longer supported, in favor of safer XDM and XDR AJAX features. AJAX-enabled sites that manually manipulate the hash of the URL may be broken by the new window.location.hash navigation property. New AJAX features like XDM have native properties that may conflict with existing custom properties. File upload control only submits the file path, not the full path, to the server. HTML or script delivered with an “image/*” MIME type is blocked from executing. Navigating a top-level frame to a site in a different security context opens a new window or tab instead of navigating within the existing frame. UTF-7 encoded script is forced into Windows-1252 encoding, which may cause plain text rendering. HTTP/HTTPS “mixed mode” pages display a dialog that defaults to displaying secure items only (as opposed to the previous nonsecure default); users may mistakenly choose to block HTTP elements, like key images. DEP/NX is on by default, blocking certain add-ons (that is, ActiveX® controls and COM objects) built with older versions of ATL from running code marked “non-executable” in memory. Content returned by a web proxy if an SSL tunnel is not established in response to a CONNECT request to the original server is blocked.	Style sheets are ignored unless they are delivered with the text/css MIME type. HTML documents delivered with a text/plain MIME type render or download as plain text only and are not MIME-sniffed to another type. SCRIPT and STYLESHEET elements reject responses with incorrect MIME types if the server sends the response header X-Content-Type-Options: nosniff. See other security updates in the Security sections of these blog posts: Internet Explorer 9 Beta minor change list Internet Explorer 9 Release Candidate minor change list
Architectural Changes Apply regardless of document or compatibility mode.	Protected Mode, also a key security feature, is enabled by default for Internet, Intranet, and Restricted Sites zones. This blocks browser extensions that could pose a security risk from running and lower privilege applications from accessing higher privilege processes (applies to Internet Explorer 7 and later on Windows Vista® and later).	Protected Mode Update: Intranet now runs in medium (instead of low) integrity level by default. Loosely Coupled IE may block add-ons (that is, ActiveX controls and COM objects) that: 1) Use windows hierarchy techniques to locate UI frame and tab windows (which now run in separate processes at different integrity levels), 2) Create a subclass of the UI frame (now at medium integrity level) from a low-integrity tab process, 3) Use unsupported messaging techniques between UI frame and tabs.