Which statement about validating markup is true?

Which statement about validating markup is true?

• A. Validation always passes when code is well-formed.
• B. Validation results are always reliable.
• C. If a validator finds an error, the remaining code on the page may fail validation, even if the remaining code is actually valid.
• D. Validation errors only occur in HTML attributes.

Answer: (C)

Validation checks markup against the rules of the document type, but a single syntax mistake can throw off how the parser reads the rest of the page. Validators often use error-recovery parsing, so once an error is found, the parser may reinterpret the following code in a way that causes more flagged issues—even if that later code is actually valid. This cascade is why you can see validation problems later in the document even when the later markup would be fine on its own. For example, a missing closing quote or tag can make the rest of the line or subsequent lines be treated as part of that error, leading to multiple false-positive issues. That’s why the statement about the remaining code failing validation despite being valid describes how validation can behave in practice. Keep in mind, well-formed syntax doesn’t guarantee conformance to all spec rules, and validation issues aren’t limited to HTML attributes—they can appear anywhere in the markup.

Validation checks markup against the rules of the document type, but a single syntax mistake can throw off how the parser reads the rest of the page. Validators often use error-recovery parsing, so once an error is found, the parser may reinterpret the following code in a way that causes more flagged issues—even if that later code is actually valid. This cascade is why you can see validation problems later in the document even when the later markup would be fine on its own. For example, a missing closing quote or tag can make the rest of the line or subsequent lines be treated as part of that error, leading to multiple false-positive issues. That’s why the statement about the remaining code failing validation despite being valid describes how validation can behave in practice.

Keep in mind, well-formed syntax doesn’t guarantee conformance to all spec rules, and validation issues aren’t limited to HTML attributes—they can appear anywhere in the markup.