ct.css — Performance Hints via Injected Stylesheet Alone

Harry's ingenious CSS technique offers performance insights by analyzing your element. A key aspect is making hidden elements visible by altering their display property—a simple yet effective trick applicable even to content. For example:

head,
head style,
head script {
  display: block;
}

Harry's brilliance shines in his sophisticated selectors, identifying performance bottlenecks based on tag usage and placement. For instance, a <script></script> tag appearing after stylesheets:

<link href="..." rel="stylesheet"><title>Page Title</title>

is inefficient, as the script execution is blocked by the CSS. While specialized performance tools can detect this, Harry leverages CSS selectors:

head [rel="stylesheet"]:not([media="print"]):not(.ct) ~ script,
head style:not(:empty) ~ script {
  /* Styles applied here for visual debugging */
}

This refined selector targets only stylesheets or style blocks that are actually causing blocking, excluding those with media="print" or the .ct class. Harry then uses styling and pseudo-elements to visually highlight these performance issues within the stylesheet itself, transforming it into a visual performance debugging tool.

This clever approach allows the stylesheet to flag various issues, including unnecessary attributes, blocking resources, and incorrectly ordered elements. The sheer ingenuity of using CSS in this way is remarkable.

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