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Notes for getting more out of the tools · calculations, metrics, CSS and work tips
Ad Metrics Made Simple | Following One Campaign All the Way Through
Instead of defining ROAS, CPA, CPC, CPM and CTR one by one, this walks a single campaign from impressions to revenue with real numbers, showing where each metric comes from and which one points at the actual problem.
Growth Rate, Fully Explained | Five Ways Reports Get It Wrong
Why growth rate, percentage change, MoM, YoY, QoQ and WoW are all one calculation, shown with real numbers, plus the traps that keep appearing in reports: asymmetric percentages, percent versus percentage points, and tiny denominators.
How Korean Take-Home Pay Is Calculated | 2026 Insurance and Tax Rates
Why gross salary and the amount landing in your account differ, worked through with real numbers using Korea's 2026 insurance rates and income tax, and how much the non-taxable amount, dependents and withholding rate actually change your net pay.
px, rem, em, %, vw | Which CSS Unit to Use and When
What CSS absolute and relative units are each relative to, how they affect accessibility and responsiveness, and which unit to reach for in each situation.
The Power of Compounding | Compound Growth and Future Value
The difference between simple and compound growth, why compound growth and future-value projection are really the same calculation, and how rate and time change the outcome dramatically: with examples.
Five JSON Syntax Errors | What to Check When One Edit Breaks Everything
The five syntax errors people actually hit when editing JSON for the first time, shown with the real error messages, plus how to read an error position and the order to check things in. No development background needed.
How QR Codes Work and How to Make Them Safely
How a QR code stores information, the difference between static and dynamic codes, balancing design against scannability, and what you must check before printing.
Merge, Split, Rotate, Delete PDF Pages | Do It Safely in the Browser
When each common PDF editing task: merge, split, rotate, delete pages: is actually needed, and why processing sensitive documents in the browser instead of uploading them to a server is the safer choice.
Character Limits | Why the Same Text Passes One Form and Fails Another
Why a form rejects your 490-character answer against a 500-character limit, explained through spaces, line breaks, emoji and byte counting, plus per-platform limits and the right order for cutting text down.