WebSlices are snippets of the entire page that a user can subscribe to.[13]

WebSlices will be automatically kept updated by the browser, and can be viewed directly from the Favorites bar, complete with graphics and visuals. Developers can mark parts of the pages as WebSlices, using the hAtom and hSlice microformat. WebSlices have been compared to Active Desktop, introduced in Internet Explorer 4 in 1997.[15]

“ The description of Active Desktop is very nearly an exact description of the new WebSlices feature in IE8. They do exactly what Active Desktop was designed to do - grab information from the Web, and display it in a kind of widget inside Internet Explorer. ” —Preston Gralla, Computer World

Activities are contextual commands that allow a user to invoke an online service from any other page.[13]

Actions such as selecting the text or other objects will give users access to the usable Activity services (such as blogging with the selected text, or viewing a map of a selected geographical location), which can then be invoked with the selected object.

According to Microsoft, Activities make copying and pasting between web pages easier.[6] IE8 specifies an XML-based encoding which allows a web application or web service to be invoked as an Activity service.

How the service will be invoked and for what categories of content it will show up is specified in the XML file.[14] Similarities have been drawn between Activities and the controversial Smart tags, feature experimented with in the IE 6 Beta but withdrawn after criticism (though later included in MS Office).[10]

Internet Explorer 8 features stricter adherence to web standards, which in some cases is incompatible with the behavior exhibited by previous versions of Internet Explorer.

As a result, web pages coded to the behavior of the older versions will break in IE8. This would have been a repetition of the situation with IE7, which having fixed a lot of bugs from IE6, broke pages which used the IE6 bugs to work around its non-compliance. This was especially a problem for offline HTML documents, which may not have been updatable (e.g. stored on a read-only medium, such as a CD-ROM or DVD-ROM).

To avoid this situation, Microsoft proposed Version Targeting whereby a page could be authored to a specific version of a browser using the X-UA-Compatible declaration either as a meta element or in the HTTP headers.[19]

A browser with a newer version than what the page has been coded for would emulate the behavior of the older version so that the assumptions the page made about the browser’s behavior holds true.

Microsoft proposed that a page with a doctype that triggers standards mode (or almost standards mode) in IE7 would by-default trigger IE7-like behavior (called “standards mode”) in IE8 and future versions of IE. The new features of IE8, along with the breaking changes, could be enabled by explicitly using the X-UA-Compatible declaration to trigger what Microsoft called the “IE8 standards mode”.

Microsoft’s reasoning was that by making the choice to opt for standards compliance explicit, pages that do not want the behavior will not trigger the IE8 standards mode.[19] IE8 standards mode could also be triggered by the HTML5 doctype. Doctypes that trigger quirks mode in IE7 will continue to do so in IE8.

The proposal was met with much controversy. Jeremy Keith, writing for A List Apart, felt that tying pages to browser versions would greatly hinder progressive development as championed by web standards.[23] Håkon Wium Lie, Chief Technology Officer of Opera Software, authors of the Opera web browser, stated in an article for The Register that the move was an example of monopolistic behaviour due to Microsoft’s dominating position in the web browser and operating system markets.[24]

Peter Bright of Ars Technica claimed that the idea of using a meta tag to pick a specific rendering mode fundamentally misses the point of standards-based development, but positioned the issue as one of idealism versus pragmatism in web development, noting that not all of the Web is actively maintained, and that, “demanding that web developers update sites to ensure they continue to work properly in any future browser version is probably too much to ask.”[25]

On March 3, 2008, Dean Hachamovitch announced that Microsoft had changed their minds, opting instead to make the IE8 standards mode (now called “standards mode”) the default in IE8 (i.e., pages with doctypes that trigger standards mode in IE7 as well as newer doctypes).[18]

Version targeting would still be present but now would be used to opt-out of progressive development and use the IE7 standards mode. While this move was praised by many of the same people who had criticised Microsoft’s original choice, including Microsoft’s competitors,[26] the subsequent release of Internet Explorer 8 Beta 1 revealed that many web sites do not work in this new standards mode.

Other new features in IE8 includes a redesigned Favorites Bar, which can now host content such as WebSlices, web feeds as well as documents, in addition to website links. The phishing filter has been augmented with Safety Filter that prevents sites known to spread malware from loading. Users need to make an explicit choice to load a blocked site; however this feature can be disabled using Group Policy. A crash recovery mechanism has been incorporated; if the browser crashes, web pages being viewed are recovered when the browser is restarted.[13] Full-page zoom now reflows the text to remove the appearance of horizontal scrollbars on zooming.[17] For developers, IE8 includes tools that allow HTML, CSS and JavaScript debugging directly from the browser.[14]

Internet Explorer 8 includes performance improvements across the HTML parser, CSS engine, mark-up tree manipulation as well as the JScript runtime and the associated garbage collector. Circular Memory leaks, which resulted earlier due to inconsistent handling of JScript objects and DOM objects, have been alleviated.[14] For better security and stability, IE8 uses the Loosely Coupled Internet Explorer (LCIE) architecture and runs the browser frame and tabs in separate processes. Glitches and hangs don’t bring down the entire browser. It also leads to higher performance and scalability. Permissions for ActiveX controls have been made more granular – instead of enabling or disabling them globally, they can now be allowed on a per-site basis.