The Old NetISSUE #9 of 60

attribute values · always quoted

Pixel PeteVSQuirks Mode

Pixel Pete saysAll attribute values must be wrapped in quotes — single or double.

HTML allows unquoted values for simple cases (width=100); XHTML never does. Every value needs quotes: width="100". This avoids ambiguity when values contain spaces or special characters and is a universally good habit even in HTML5.

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Quote every attribute value
Single or double quotes both fine
Prevents space/character ambiguity
Good style in HTML5 too

Quirks Mode attacks — common mistakes

Unquoted numeric values
Mismatched opening/closing quote types
Forgetting quotes on boolean-like attributes

Boss battleAdd quotes to every unquoted attribute in a snippet.

Example code

<!doctype html><html><head><meta charset="utf-8"></head>
<body style="background:#06040d;color:#e6e0ff;font-family:monospace;padding:20px"><pre>invalid: &lt;td colspan=2 width=100&gt;
valid:   &lt;td colspan="2" width="100"&gt;</pre></body></html>

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