Why does IE9 switch to compatibility mode on my website?
Avoid IE9 compatibility mode by starting your HTML with the correct DOCTYPE and adding a meta tag for X-UA-Compatible. Insert this snippet at the top:
The DOCTYPE declaration should be the first line in your HTML and the meta tag should be in the <head> section, forcing IE9 to use the most recent rendering engine.
Implement the right standards
IE9, similar to older versions, can switch to different rendering modes depending on your DOCTYPE declaration as well as certain HTML/CSS patterns. Forcing an incorrect compatibility mode, such as X-UA-Compatible set incorrectly or missing, potentially puts IE9 in compatibility mode, disrupting your website's layout.
Ensure modern web standards compliance
Adhere to web standards to ensure that your website renders correctly across all browsers, including IE9. Avoid deprecated HTML and CSS, and use feature-sniffing instead of browser-sniffing to provide functionality. Unlike browser-sniffing, feature-sniffing detects if a browser supports a certain feature, providing a more versatile and future-oriented solution.
Monitor browser and user settings
IE9 could enter compatibility mode due to user settings or browser behavior, for instance, if a user previously selected 'compatibility view' for your site. Overrule this by asking users to adjust their settings under Tools -> Compatibility view settings or by removing your site from Microsoft's compatibility view list.
Leverage HTTP headers for an edge
While the X-UA-Compatible meta tag is essential, it's equally important to specify the same value as an HTTP header. This ensures your compatibility settings are respected regardless of the HTTP response, ensuring more reliable rendering.
Decoding intranet defaults and invisible menus
IE9 may default to compatibility mode for intranet sites. Inform users to press Alt to access IE's hidden menu enabling them to amend compatibility settings if necessary. Place meta tags correctly to ensure your website isn't listed on Microsoft's compatibility view list.
Debugging compatibility mode troubles
It isn't always an easy task to prevent IE9 from switching to compatibility mode. If adding the X-UA-Compatible tag doesn't do the trick, you can:
- Remove CSS Includes: Take out any CSS files temporarily to determine whether a particular stylesheet is causing the issue.
- Test for HTML5 Support: Determine whether the HTML5 capabilities of IE9 are sufficient for your site and use fallback methods where necessary.
- Avoid Conditional Comments: These comments may trick IE9 into switching to an older document mode. Handle them with care!
- Manual Overrides: Ever heard of a quick fix? Configuring these settings to disable certain modes in the browser might be just the ticket.
Looking ahead
It's important to fix compatibility issues, but remember to urge users to upgrade their browsers to more current versions with superior HTML5 support. This not only improves your users' browsing experience but also simplifies developers' tasks by minimizing the need to cater to outdated rendering engines.
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