Visualforce Developer Guide

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Introducing Visualforce
Tools for Visualforce Development
Getting a Quick Start with Visualforce
Customizing the Appearance and Output of Visualforce Pages
Styling Visualforce Pages
HTML Comments and IE Conditional Comments
HTML Tags Added or Modified by Visualforce
Using a Custom Doctype
Change the MIME type of Your Visualforce Page
Setting Custom HTML Attributes on Visualforce Components
Render a Visualforce Page as a PDF File
Standard Controllers
Standard List Controllers
Custom Controllers and Controller Extensions
Advanced Examples
Override Buttons, Links, and Tabs with Visualforce
Using Static Resources
Creating and Using Custom Components
Dynamic Visualforce Bindings
Dynamic Visualforce Components
Integrate Email with Visualforce
Visualforce Charting
Creating Maps with Visualforce
Render Flows with Visualforce
Templating with Visualforce
Developing Salesforce Apps with Visualforce
Adding Visualforce to a Salesforce AppExchange App
Using JavaScript in Visualforce Pages
Communicating Across the DOM with Lightning Message Service
Visualforce Best Practices
Standard Visualforce Component Reference
Appendices
PDF

HTML Comments and IE Conditional Comments

Visualforce removes most HTML and XML comments from the page before rendering, without processing their contents. Internet Explorer conditional comments, however, won’t be removed, allowing you to include IE-specific resources and meta tags.

Visualforce doesn’t evaluate anything enclosed within standard HTML comments (<!-- -->), whether the comments are single line or multiline. For non-Internet Explorer comments, the Visualforce compiler replaces the contents of the HTML comment with asterisks. This replacement makes HTML comments unsuitable for commenting out JavaScript code in older browsers.

Internet Explorer conditional comments are most commonly used to address browser compatibility issues, generally with older versions of IE. Although conditional comments work wherever they’re used on the page, they’re frequently placed inside the page’s <head> tags, where they can be used to include version-specific stylesheets or JavaScript compatibility “shims.”

To place conditional comments inside a page’s <head> tag, disable the standard Salesforce header, sidebar, and stylesheets, and add your own <head> and <body> tags:
<apex:page docType="html-5.0" showHeader="false" standardStylesheets="false">
    <head>
      <!-- Base styles -->
      <apex:stylesheet value="{!URLFOR($Resource.BrowserCompatibility, 'css/style.css')}"/>
        
      <!--[if lt IE 7]>
          <script type="text/javascript" 
              src="{!URLFOR($Resource.BrowserCompatibility, 'js/obsolete-ie-shim.js')}>
          </script>
          <link rel="stylesheet" type="text/css" 
              href="{!URLFOR($Resource.BrowserCompatibility, 'css/ie-old-styles.css')}" />
      <![endif]--> 
    
      <!--[if IE 7]>
          <link rel="stylesheet" type="text/css" 
              href="{!URLFOR($Resource.BrowserCompatibility, 'css/ie7-styles.css')}" />
      <![endif]-->
    </head>

    <body>
        <h1>Browser Compatibility</h1>
        <p>It's not just a job. It's an adventure.</p>
    </body>
</apex:page>
Visualforce doesn’t support or evaluate Visualforce tags, for example, <apex:includeScript/>, within standard HTML comments. However, it will evaluate the following expressions within IE conditional comments:
  • Global variables, such as $Resource and $User
  • The URLFOR() function

See Microsoft’s documentation for Internet Explorer conditional comments for further details of how to use them.