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Practical guides covering developer tools, health metrics, SEO, converters and more — written to be actually useful.
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Your List Still Has Duplicates After Removing Duplicates
Your Headings Are the Only Part Most Readers Read
Strip a page down to its headings and you get the outline readers are actually skimming. If it doesn't stand alone as an argument, the page probably doesn't either.
Your Height Isn't One Number: Measurement Variation Explained
You're 1–2 cm taller in the morning, and "5.9" means two different heights. Why height is a measurement with error bars, and how to take a consistent one.
Why Comparing Hashes With == Leaks Your Secret
Comparing a signature with === leaks it one byte at a time, and hash(secret + message) can be forged without the secret. Two one-line fixes for both.
The Vary Header: Why Your Cache Serves the Wrong Content
The Vary header decides what counts as the same request to a cache. Missing it serves wrong content; overusing it destroys your hit rate. Here's how to get it right.
The Invisible HTML Entities: nbsp, shy and Zero-Width Spaces
Non-breaking spaces, soft hyphens and zero-width spaces control how text wraps — and they're invisible in your source. Why entity form matters and where each belongs.
Drag Rises With Speed Squared: The Real Cost of 130 km/h
Aerodynamic drag rises with the square of speed, so the last 20 km/h of motorway cruising costs far more than the first. The physics behind fuel economy at speed.
Why Wheels Spin Backwards on Film: Aliasing and Nyquist
Sample too slowly and frequencies don't disappear — they fold back and appear as signals that were never there. The Nyquist limit, aliasing, and why filters go first.
Word Boundaries and Lookarounds: Precise Find & Replace
Replacing "id" also hits valid, hidden and width. Word boundaries, lookarounds and lazy quantifiers are the three patterns that make find-and-replace precise.
Why a Kettle Is 95% Efficient and a Power Station Is 45%
A kettle is 95% efficient and a power station is 45%. That's not engineering quality — it's the second law of thermodynamics, and it explains heat pumps too.
Flat Rate vs Reducing Balance: The Same 7% Costs Double
A "7% flat rate" loan costs nearly double a 7% reducing-balance loan. Here's how to spot flat-rate quoting, what APR actually includes, and how to compare offers.
Your Due Date Is a Distribution, Not a Deadline
Only about 4% of babies arrive on their due date. Here's what the birth timing distribution actually looks like, why early term and full term differ, and how to plan.
Why 31 January Plus One Month Has No Right Answer
Adding one month to 31 January has no correct answer, and "add one day" isn't "add 24 hours". The date arithmetic edge cases that break calendars and billing systems.
