Question 1

How do I check HTML/CSS code?

Accepted Answer

Select HTML or CSS at the top right of the input area, paste your code, and click "Check". Errors and warnings are listed line by line with fix suggestions.

Question 2

What does the checker cover?

Accepted Answer

Tag pairing and self-closing recognition, DOCTYPE and html/head/body required structure, HTML entity escaping, attribute quotes, CSS brace and semicolon pairing, !important usage hints, and basic selector checks.

Question 3

Does passing mean my code is perfect?

Accepted Answer

No. This tool performs basic structural checks; it is not equivalent to full W3C validation and does not guarantee rendering across browsers. Semantic correctness still needs human review.

Question 4

What are the known limitations?

Accepted Answer

Quote checks may false-positive when attribute values contain the > character; complex template syntax such as JSX or template engines is out of scope.

Question 5

Can "Simple Format" replace prettier?

Accepted Answer

No. It only does basic line-break cleanup and may break content that preserves formatting, such as <pre>. Use a dedicated code formatter for full formatting.

Question 6

How do I fix reported errors?

Accepted Answer

Each error shows its line number, rule, and a fix suggestion. Fix from top to bottom and re-check until it passes.