Back in the early days of computers, programmers used a text editor where they had to type a short code to find text.
That code was g/re/p, which literally meant:
Globally (search everywhere...)
Regular Expression (for a specific pattern)
Print (..and show it on the screen).
People loved that specific function so much that they turned it into its own standalone tool and named it grep.
Today, tech folks even use it as a verb;
If someone says, "Let me grep the logs," they just mean, "Let me quickly search through these files to find the issue."
The 'window.innerHeight' property returns the interior height of a browser window's content area (the layout viewport) in pixels. useful when want to know the vh/viewport width and height of local devise for responsiveness.
1.
LCP (Largest Contentful Paint) = how fast does the main thing appear
So what?
Users feel it, they see half-built page, more of them leave.
Tip
Preload the poster: if it loads late, the LCP score gets worse
<link rel="preload" as="img" href="/hero.webp" fetchpriority="high">
2.
CLS(Cumulative Layout Shift) = does anything jump/page jumps
So what?
Misclicks, lost place, pages feel unfinished
Tip
If the poster is 16:9 & the video is 4:3, page shifts when they swap after load, that adds to the CLS.
Matching the aspect ratio keeps the layout still.
Letter spacing or line spacing (line-height) is tied to the element's own computed font-size generally.
So, in calculation, 1 em equals the font size of the element it is applied to.
*, p, .menu-item, #main-header, div p, ul > li, h1 + p, h1 ~ p, a[target], input[type="text"], a[href^="https"], a[href$=".pdf"], button:hover, li:nth-child(odd), p::before, h1, h2, h3, button.primary are all examples of CSS selectors.
Learning to walk before the run.
So the plumbing (WebMCP) is invisible.
But the trust layer around it,
consent screens,
permission settings,
clear receipts of what an agent did;
is very much a human design problem.