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Hướng dẫn, bài học và mẹo để tận dụng tối đa các công cụ trực tuyến miễn phí. 194 bài viết.
194 articles — page 2 of 9
The French Republic Abolished Sundays in 1793 and Renamed Every Month. Here Is the 13-Year Experiment.
In 1793, France replaced the entire Gregorian calendar with 10-day weeks and nature-named months. Napoleon abolished it in 1806. Here is what failed and why.
Developers Read Code Ten Times More Than They Write It. Here Is Where Explanation Actually Helps.
Developers spend ten hours reading code for every hour writing it. Here are the specific situations where a plain-English code explainer earns its place.
16:9 Was Not Chosen Because It Looks Best. It Was Chosen Because It Wastes the Least Screen Area.
In 1984, mathematician Kerns Powers found that 16:9 was the geometric mean of all common film and TV ratios. That compromise is on every screen you own today.
Natural Language Is Ambiguous. SQL Is Not. Here Is How AI Bridges the Two.
SQL was designed in the 1970s to be readable by non-programmers. Here is why its declarative structure makes it unusually good for AI to generate from natural language.
Two Funds Both Returned 8 Percent. Standard Deviation Shows They Were Not Even Close.
Two investments with identical average returns can have completely different risk profiles. Standard deviation is the calculation that reveals the difference.
SVG Files Are Math. PNG Files Are Pixels. Here Is What Converting Between Them Actually Does.
SVG vector graphics describe shapes mathematically. Converting to PNG rasterizes them into pixels. Here's what that process does, why resolution matters, and when you need it.
The Kubernetes Config That Broke on a Tab. Why YAML Converts to JSON Before Reaching Systems.
YAML's readability comes with whitespace fragility. Here is why configuration written in YAML gets converted to JSON before reaching APIs and services.
Your Gross Margin Is 40%. Your Net Margin Is 3%. Which One Should You Be Watching?
Gross margin and net margin measure different things. Understanding the gap between them is where business performance analysis actually starts.
PDF Passwords Were Broken in 1998. Here Is How the Encryption Evolved Since Then.
PDF encryption started with 40-bit RC4 restricted by US export law and evolved to AES-256 by 2017. The history of how PDF password protection changed over 30 years.
The Protocol That Ran the Internet for 28 Years Without Being a Standard
The robots.txt Robots Exclusion Protocol ran every major crawler from 1994 until the IETF finally published RFC 9309 in 2022. Here is what changed and what stayed ambiguous.
You Are Probably Overestimating How Much You Need to Save Each Month
Dividing your savings goal by months gives the wrong answer once interest is in the picture. Here is how compound interest reduces what you actually need to save.
Deadlines Described in Months Feel Far Away. Here Is Why Days Work Better.
Behavioral research shows people act faster on deadlines expressed in days than months, even when the time remaining is identical. Here is why the unit matters.
A Valid Email Address Can Still Bounce. Here Are the Three Layers of Validation and What Each One Catches.
Email validation has three layers: syntax, domain DNS, and mailbox existence. Tools can verify the first two. The third is blocked by major providers to prevent address scraping.
JSON Was Designed for Machines. YAML Was Designed for People. Here Is Why That Matters for Configuration Files.
JSON requires quotes on every key and precise trailing commas. YAML removes that friction. Here is why teams convert JSON configs to YAML for team maintenance.
Your Hard Drive Is Smaller Than Advertised. Here Is Why That Is Legal, Expected, and Entirely the Result of a 1950s Naming Convention.
A kilobyte is 1,000 bytes to hard drive makers and 1,024 bytes to your OS. This naming dispute from the 1950s still shrinks every drive you buy. Here is the full story.
Hans Peter Luhn Filed a Patent to Catch Punch Card Errors in 1954. It Now Validates Every Credit Card on Earth.
Luhn's 1954 IBM patent was designed to catch transcription errors on punch cards. His mod-10 formula now validates every Visa, Mastercard, and Amex number worldwide.
The Designer Approved the Red. The Printer Matched the File. The Color Was Still Wrong. Here Is Why.
HEX colors exist in sRGB, which can't reproduce all Pantone colors. Screen colors are emissive. Print colors are reflective. Here is how color spaces explain the gap.
Twitter Doubled the Character Limit to 280. Only 1 Percent of Tweets Used the Extra Space.
Twitter's 140-character limit came from SMS text message constraints, not writing research. When it doubled to 280 in 2017, only 1% of tweets used the extra space.
Why Every Computer in the World Counts from January 1, 1970 -- And What Breaks in 2038
Unix time started at January 1, 1970 by pragmatic accident. The same 32-bit integer choice that made it compact is what causes an overflow at 03:14:07 on January 19, 2038.
UTM Stands for Urchin. The Company Was Named After Sea Urchins. Google Bought It in 2005 and Kept the Name.
Urchin Software built UTM tracking in 2002. Google acquired it for $30M in 2005 and kept the parameter names. Here is what each of the five parameters actually tracks.
WebP Transparency vs PNG Transparency: They Are Not the Same Thing
WebP and PNG both support transparency, but they behave differently outside browsers. Here's when to stick with PNG and when WebP actually wins.
John Gruber Left the Edge Cases Undefined in 2004. The Spec Wars That Followed Lasted a Decade.
John Gruber published Markdown in 2004 with intentional ambiguities. The incompatible parsers that followed took a decade and a 100-page spec to resolve.
Rotating a PDF Page Does Not Move a Single Pixel. Here Is What Actually Changes in the File.
When you rotate a PDF page, no pixels move. The /Rotate key in the page dictionary changes instead. Here is why that matters for printing and workflows.
The Blog Migration Looked Successful. Six Weeks Later Traffic Was Down 35 Percent. The Redirects Were Wrong.
A 302 redirect transfers no authority. A 3-hop 301 chain loses 27% of link equity. Here is how to audit redirects before a site migration costs you months of rankings.