HTML 5.2: 1. Introduction

When accepting untrusted input, e.g., user-generated content such as text comments, values in URL parameters, messages from third-party sites, etc, it is imperative that the data be validated before use, and properly escaped when displayed. Failing to do t

www.w3.org

A Complete Guide to Flexbox | CSS-Tricks

Our comprehensive guide to CSS flexbox layout. This complete guide explains everything about flexbox, focusing on all the different possible properties for the parent element (the flex container) and the child elements (the flex items). It also includes hi

css-tricks.com

Color Tool - Material Design

Create and share color palettes for your UI, and measure the accessibility of any color combination.

material.io

Flexbox Froggy

A game for learning CSS flexbox

flexboxfroggy.com

CSS Diner

A fun game to help you learn and practice CSS selectors.

flukeout.github.io

C 언어 코딩 도장: 21.4 조건식과 논리 연산자 사용하기

값뿐만 아니라 조건식 자체도 논리 연산자로 판단할 수 있습니다. cond_exp_logical_operator.c #include int main() { int num1 = 20; int num2 = 10; int num3 = 30; int num4 = 15; printf("%d\n", num1 > num2 && num3 > num4); // 1: 양쪽 �

dojang.io

HTML elements reference

This page lists all the HTML elements, which are created using tags.

developer.mozilla.org

The W3C Markup Validation Service

Validate by File Upload Note: file upload may not work with Internet Explorer on some versions of Windows XP Service Pack 2, see our information page on the W3C QA Website.

validator.w3.org

JS Bin

Sample of the bin:

jsbin.com

Can I use... Support tables for HTML5, CSS3, etc

About "Can I use" provides up-to-date browser support tables for support of front-end web technologies on desktop and mobile web browsers. The site was built and is maintained by Alexis Deveria, with occasional updates provided by the web development commu

caniuse.com