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Event 1049 - Standards Mode

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Applies To: Windows 7, Windows Vista

To adhere to the latest Web standards, Windows® Internet Explorer® 8 includes an update to the standards mode engine. The standards mode engine is enabled when a standards mode DOCTYPE declaration is found in the HTML source of a Web page. In standards mode, many components that affect the layout and rendering of Web pages have been changed, including HTML and Cascading Style Sheets (CSS) interpretation, document object model APIs, Microsoft® JScript® performance and security, and accessibility APIs.

What is Standards Mode?

Each major release of Internet Explorer adds features designed to make the browser easier to use, to increase security, and to more closely support industry standards. As Internet Explorer gains features, there is a risk that older Web sites may not be displayed correctly. To minimize this risk, Internet Explorer 8 supports a number of document compatibility modes that enable different features and can affect the way content is displayed:

  • IE5 mode renders content as if it were displayed by using quirks mode in Internet Explorer 7, which is very similar to the way content was displayed in Microsoft Internet Explorer 5.

  • IE7 mode renders content as if it were displayed by using the standards mode in Microsoft Internet Explorer 7, regardless whether the page contains a <!DOCTYPE> directive.

  • Emulate IE7 mode tells Internet Explorer to behave like Internet Explorer 7, without providing any additional hints regarding the compatibility mode. In this case, the browser uses the <!DOCTYPE> directive of the Web page to determine how to render content:

    • Standards mode directives are displayed by using the Internet Explorer 7 standards mode.

    • Quirks mode directives are displayed by using the Internet Explorer 5 mode. Unlike the Internet Explorer 7 mode, Emulate IE7 mode respects the <!DOCTYPE> directive.

  • IE8 mode provides the highest support available for industry standards, including support for the W3C Cascading Style Sheets Level 2.1 Specification, the W3C Selectors API, and limited support for the W3C Cascading Style Sheets Level 3 Specification.

  • Emulate IE8 mode tells Internet Explorer to use the <!DOCTYPE> directive of the Web page to determine how to render the content. Standards-mode directives are displayed in IE8 standards mode and quirks-mode directives are displayed in quirks mode.

  • Edge mode tells Internet Explorer to display content in the highest mode available. With Internet Explorer 8, this is equivalent to IE8 mode. If a future release of Internet Explorer supported a higher compatibility mode, then pages set to edge mode would appear in the highest mode supported by that version. Those same pages would still appear in IE8 mode when viewed with Internet Explorer 8.

By default, Internet Explorer 8 renders Internet sites in IE8 standards mode and intranet sites in IE7 emulation mode. Because Internet pages automatically default to standards mode, users may experience issues with Web pages that do not explicitly opt-in to that mode. You can enable a page to explicitly opt-in to standards mode by using one of the following techniques:

  • Including a meta tag on the page that specifies IE=8 or IE=EmulateIE8.

  • Configuring your Web server to send a compatibility header that includes the page that specifies IE=8 or IE=EmulateIE8.

We recommend that you warn users that a Web page might not be displayed properly if the page does not explicitly opt-in to IE8 standards mode.

When Is This Event Logged?

This event is logged if a Web page does not explicitly opt-in to IE8 standards mode, but still complies with all the specifications of IE8 standards mode. For example, an event will be logged if the Web page does not explicitly include a meta tag that specifies IE8 emulation mode.

Note

For more information and examples, see the Event 1049-Standards Mode topic from Internet Explorer Application Compatibility.

Remediation

You can insert a meta tag into your Web page, or add an HTTP header at the Web site-level, which explicitly indicates that IE8 standards mode should be used to render the Web page. For example, in an ASP.NET application, you can use the following Web.config file to set the compatibility header for the corresponding application.

<system.webServer>
    <httpProtocol>
      <customHeaders>
        <clear />
        <add name="X-UA-Compatible" value="IE=IE8" />
      </customHeaders>
    </httpProtocol>
</system.webServer>

Or you can add the following meta tag directory to your Web page:

<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE8" />

Important

The value of IE can be IE8 or EmulateIE8, either value will enable the application or Web page to opt-in to IE8 standards mode.

See Also

Concepts

Known Internet Explorer Security Feature Issues