error.css

body { background-color: #fff; color: #222; font: 16px/1.5 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif; margin: 0; }
.container { margin: 30px; max-width: 600px; }
h1 { color: #dc3545; font-size: 24px; }
h2 { font-size: 18px; }

File

vendor/symfony/error-handler/Resources/assets/css/error.css

View source 
  1. body { background-color: #fff; color: #222; font: 16px/1.5 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif; margin: 0; }

  2. .container { margin: 30px; max-width: 600px; }

  3. h1 { color: #dc3545; font-size: 24px; }

  4. h2 { font-size: 18px; }