From MozillaZine Knowledge Base

View Source allows viewing the HTML, CSS, JavaScript, etc. code that is used to generate any given page.

UI

• View→Page Source.
• Clicking on the link for an error or warning in the JavaScript Console.
• Navigating to a URL of the form view-source://example.com.
• Right click the content area→View Page Source or This Frame→View Frame Source.

View Selection Source

When selecting parts of a page and right-clicking, the option "View Selection Source" comes up in the context menu. This will open a View Source window that will contain the code of the selection and any relevant surrounding code. This code may or may not be the same as the original source because it has passed through Mozilla's parser and may have been created or changed dynamically by JavaScript.

Articles in category "View Source"

V

• View source.editor.external
• View source.editor.path
• View source.syntax highlight
• View source.wrap long lines