HTML 编码（字符集）
为了正确显示 HTML 页面，Web 浏览器必须知道要使用哪个字符集。
1. 从 ASCII 到 UTF-8
ASCII 是第一个字符编码标准。ASCII 定义了 128 种可以在互联网上使用的字符：数字（0-9）、英文字母（A-Z）和一些特殊字符，比如：! $ + - ( ) @ < >。
ISO-8859-1 是 HTML 4 的默认字符集。此字符集支持 256 个不同的字符代码。HTML 4 同时支持 UTF-8。
ANSI（Windows-1252）是原始的 Windows 字符集。 ANSI 与 ISO-8859-1 相同，不同之处在于 ANSI 具有 32 个额外的字符。
HTML5 规范鼓励 Web 开发人员使用 UTF-8 字符集，该字符集涵盖了世界上几乎所有的字符和符号！
. HTML charset 属性
为了正确显示 HTML 页面，Web 浏览器必须了解页面中使用的字符集。
这在 <meta> 标签中指定：
<meta charset="UTF-8">
2. 字符集之间的差异
下表展示了上述字符集之间的区别：
| Numb | ASCII | ANSI | 8859 | UTF-8 | Description |
|---|---|---|---|---|---|
| 32 | space | ||||
| 33 | ! | ! | ! | ! | exclamation mark |
| 34 | " | " | " | " | quotation mark |
| 35 | # | # | # | # | number sign |
| 36 | $ | $ | $ | $ | dollar sign |
| 37 | % | % | % | % | percent sign |
| 38 | & | & | & | & | ampersand |
| 39 | ' | ' | ' | ' | apostrophe |
| 40 | ( | ( | ( | ( | left parenthesis |
| 41 | ) | ) | ) | ) | right parenthesis |
| 42 | * | * | * | * | asterisk |
| 43 | + | + | + | + | plus sign |
| 44 | , | , | , | , | comma |
| 45 | - | - | - | - | hyphen-minus |
| 46 | . | . | . | . | full stop |
| 47 | / | / | / | / | solidus |
| 48 | 0 | 0 | 0 | 0 | digit zero |
| 49 | 1 | 1 | 1 | 1 | digit one |
| 50 | 2 | 2 | 2 | 2 | digit two |
| 51 | 3 | 3 | 3 | 3 | digit three |
| 52 | 4 | 4 | 4 | 4 | digit four |
| 53 | 5 | 5 | 5 | 5 | digit five |
| 54 | 6 | 6 | 6 | 6 | digit six |
| 55 | 7 | 7 | 7 | 7 | digit seven |
| 56 | 8 | 8 | 8 | 8 | digit eight |
| 57 | 9 | 9 | 9 | 9 | digit nine |
| 58 | : | : | : | : | colon |
| 59 | ; | ; | ; | ; | semicolon |
| 60 | < | < | < | < | less-than sign |
| 61 | = | = | = | = | equals sign |
| 62 | > | > | > | > | greater-than sign |
| 63 | ? | ? | ? | ? | question mark |
| 64 | @ | @ | @ | @ | commercial at |
| 65 | A | A | A | A | Latin capital letter A |
| 66 | B | B | B | B | Latin capital letter B |
| 67 | C | C | C | C | Latin capital letter C |
| 68 | D | D | D | D | Latin capital letter D |
| 69 | E | E | E | E | Latin capital letter E |
| 70 | F | F | F | F | Latin capital letter F |
| 71 | G | G | G | G | Latin capital letter G |
| 72 | H | H | H | H | Latin capital letter H |
| 73 | I | I | I | I | Latin capital letter I |
| 74 | J | J | J | J | Latin capital letter J |
| 75 | K | K | K | K | Latin capital letter K |
| 76 | L | L | L | L | Latin capital letter L |
| 77 | M | M | M | M | Latin capital letter M |
| 78 | N | N | N | N | Latin capital letter N |
| 79 | O | O | O | O | Latin capital letter O |
| 80 | P | P | P | P | Latin capital letter P |
| 81 | Q | Q | Q | Q | Latin capital letter Q |
| 82 | R | R | R | R | Latin capital letter R |
| 83 | S | S | S | S | Latin capital letter S |
| 84 | T | T | T | T | Latin capital letter T |
| 85 | U | U | U | U | Latin capital letter U |
| 86 | V | V | V | V | Latin capital letter V |
| 87 | W | W | W | W | Latin capital letter W |
| 88 | X | X | X | X | Latin capital letter X |
| 89 | Y | Y | Y | Y | Latin capital letter Y |
| 90 | Z | Z | Z | Z | Latin capital letter Z |
| 91 | [ | [ | [ | [ | left square bracket |
| 92 | \ | \ | \ | \ | reverse solidus |
| 93 | ] | ] | ] | ] | right square bracket |
| 94 | ^ | ^ | ^ | ^ | circumflex accent |
| 95 | _ | _ | _ | _ | low line |
| 96 | ` | ` | ` | ` | grave accent |
| 97 | a | a | a | a | Latin small letter a |
| 98 | b | b | b | b | Latin small letter b |
| 99 | c | c | c | c | Latin small letter c |
| 100 | d | d | d | d | Latin small letter d |
| 101 | e | e | e | e | Latin small letter e |
| 102 | f | f | f | f | Latin small letter f |
| 103 | g | g | g | g | Latin small letter g |
| 104 | h | h | h | h | Latin small letter h |
| 105 | i | i | i | i | Latin small letter i |
| 106 | j | j | j | j | Latin small letter j |
| 107 | k | k | k | k | Latin small letter k |
| 108 | l | l | l | l | Latin small letter l |
| 109 | m | m | m | m | Latin small letter m |
| 110 | n | n | n | n | Latin small letter n |
| 111 | o | o | o | o | Latin small letter o |
| 112 | p | p | p | p | Latin small letter p |
| 113 | q | q | q | q | Latin small letter q |
| 114 | r | r | r | r | Latin small letter r |
| 115 | s | s | s | s | Latin small letter s |
| 116 | t | t | t | t | Latin small letter t |
| 117 | u | u | u | u | Latin small letter u |
| 118 | v | v | v | v | Latin small letter v |
| 119 | w | w | w | w | Latin small letter w |
| 120 | x | x | x | x | Latin small letter x |
| 121 | y | y | y | y | Latin small letter y |
| 122 | z | z | z | z | Latin small letter z |
| 123 | { | { | { | { | left curly bracket |
| 124 | | | | | | | | | vertical line |
| 125 | } | } | } | } | right curly bracket |
| 126 | ~ | ~ | ~ | ~ | tilde |
| 127 | DEL | ||||
| 128 | euro sign | ||||
| 129 | NOT USED | ||||
| 130 | single low-9 quotation mark | ||||
| 131 | Latin small letter f with hook | ||||
| 132 | double low-9 quotation mark | ||||
| 133 | horizontal ellipsis | ||||
| 134 | dagger | ||||
| 135 | double dagger | ||||
| 136 | modifier letter circumflex accent | ||||
| 137 | per mille sign | ||||
| 138 | Latin capital letter S with caron | ||||
| 139 | single left-pointing angle quotation mark | ||||
| 140 | Latin capital ligature OE | ||||
| 141 | NOT USED | ||||
| 142 | Latin capital letter Z with caron | ||||
| 143 | NOT USED | ||||
| 144 | NOT USED | ||||
| 145 | left single quotation mark | ||||
| 146 | right single quotation mark | ||||
| 147 | left double quotation mark | ||||
| 148 | right double quotation mark | ||||
| 149 | bullet | ||||
| 150 | en dash | ||||
| 151 | em dash | ||||
| 152 | small tilde | ||||
| 153 | trade mark sign | ||||
| 154 | Latin small letter s with caron | ||||
| 155 | single right-pointing angle quotation mark | ||||
| 156 | Latin small ligature oe | ||||
| 157 | NOT USED | ||||
| 158 | Latin small letter z with caron | ||||
| 159 | Latin capital letter Y with diaeresis | ||||
| 160 | no-break space | ||||
| 161 | ! | ! | ! | inverted exclamation mark | |
| 162 | c | c | c | cent sign | |
| 163 | lb | lb | lb | pound sign | |
| 164 | ¤ | ¤ | ¤ | currency sign | |
| 165 | yen | yen | yen | yen sign | |
| 166 | | | | | | | broken bar | |
| 167 | § | § | § | section sign | |
| 168 | ¨ | ¨ | ¨ | diaeresis | |
| 169 | (c) | (c) | (c) | copyright sign | |
| 170 | a | a | a | feminine ordinal indicator | |
| 171 | << | << | << | left-pointing double angle quotation mark | |
| 172 | not | not | not | not sign | |
| 173 | - | - | - | soft hyphen | |
| 174 | (R) | (R) | (R) | registered sign | |
| 175 | macron | ||||
| 176 | ° | ° | ° | degree sign | |
| 177 | ± | ± | ± | plus-minus sign | |
| 178 | ^2 | ^2 | ^2 | superscript two | |
| 179 | ^3 | ^3 | ^3 | superscript three | |
| 180 | ' | ' | ' | acute accent | |
| 181 | u | u | u | micro sign | |
| 182 | P | P | P | pilcrow sign | |
| 183 | · | · | · | middle dot | |
| 184 | , | , | , | cedilla | |
| 185 | ^1 | ^1 | ^1 | superscript one | |
| 186 | o | o | o | masculine ordinal indicator | |
| 187 | >> | >> | >> | right-pointing double angle quotation mark | |
| 188 | 1/4 | 1/4 | 1/4 | vulgar fraction one quarter | |
| 189 | 1/2 | 1/2 | 1/2 | vulgar fraction one half | |
| 190 | 3/4 | 3/4 | 3/4 | vulgar fraction three quarters | |
| 191 | ? | ? | ? | inverted question mark | |
| 192 | `A | `A | `A | Latin capital letter A with grave | |
| 193 | 'A | 'A | 'A | Latin capital letter A with acute | |
| 194 | ^A | ^A | ^A | Latin capital letter A with circumflex | |
| 195 | ~A | ~A | ~A | Latin capital letter A with tilde | |
| 196 | "A | "A | "A | Latin capital letter A with diaeresis | |
| 197 | A | A | A | Latin capital letter A with ring above | |
| 198 | AE | AE | AE | Latin capital letter AE | |
| 199 | C | C | C | Latin capital letter C with cedilla | |
| 200 | `E | `E | `E | Latin capital letter E with grave | |
| 201 | 'E | 'E | 'E | Latin capital letter E with acute | |
| 202 | ^E | ^E | ^E | Latin capital letter E with circumflex | |
| 203 | "E | "E | "E | Latin capital letter E with diaeresis | |
| 204 | `I | `I | `I | Latin capital letter I with grave | |
| 205 | 'I | 'I | 'I | Latin capital letter I with acute | |
| 206 | ^I | ^I | ^I | Latin capital letter I with circumflex | |
| 207 | "I | "I | "I | Latin capital letter I with diaeresis | |
| 208 | D | D | D | Latin capital letter Eth | |
| 209 | ~N | ~N | ~N | Latin capital letter N with tilde | |
| 210 | `O | `O | `O | Latin capital letter O with grave | |
| 211 | 'O | 'O | 'O | Latin capital letter O with acute | |
| 212 | ^O | ^O | ^O | Latin capital letter O with circumflex | |
| 213 | ~O | ~O | ~O | Latin capital letter O with tilde | |
| 214 | "O | "O | "O | Latin capital letter O with diaeresis | |
| 215 | × | × | × | multiplication sign | |
| 216 | O | O | O | Latin capital letter O with stroke | |
| 217 | `U | `U | `U | Latin capital letter U with grave | |
| 218 | 'U | 'U | 'U | Latin capital letter U with acute | |
| 219 | ^U | ^U | ^U | Latin capital letter U with circumflex | |
| 220 | "U | "U | "U | Latin capital letter U with diaeresis | |
| 221 | 'Y | 'Y | 'Y | Latin capital letter Y with acute | |
| 222 | Th | Th | Th | Latin capital letter Thorn | |
| 223 | ss | ss | ss | Latin small letter sharp s | |
| 224 | à | à | à | Latin small letter a with grave | |
| 225 | á | á | á | Latin small letter a with acute | |
| 226 | ^a | ^a | ^a | Latin small letter a with circumflex | |
| 227 | ~a | ~a | ~a | Latin small letter a with tilde | |
| 228 | "a | "a | "a | Latin small letter a with diaeresis | |
| 229 | a | a | a | Latin small letter a with ring above | |
| 230 | ae | ae | ae | Latin small letter ae | |
| 231 | c | c | c | Latin small letter c with cedilla | |
| 232 | è | è | è | Latin small letter e with grave | |
| 233 | é | é | é | Latin small letter e with acute | |
| 234 | ê | ê | ê | Latin small letter e with circumflex | |
| 235 | "e | "e | "e | Latin small letter e with diaeresis | |
| 236 | ì | ì | ì | Latin small letter i with grave | |
| 237 | í | í | í | Latin small letter i with acute | |
| 238 | ^i | ^i | ^i | Latin small letter i with circumflex | |
| 239 | "i | "i | "i | Latin small letter i with diaeresis | |
| 240 | d | d | d | Latin small letter eth | |
| 241 | ~n | ~n | ~n | Latin small letter n with tilde | |
| 242 | ò | ò | ò | Latin small letter o with grave | |
| 243 | ó | ó | ó | Latin small letter o with acute | |
| 244 | ^o | ^o | ^o | Latin small letter o with circumflex | |
| 245 | ~o | ~o | ~o | Latin small letter o with tilde | |
| 246 | "o | "o | "o | Latin small letter o with diaeresis | |
| 247 | ÷ | ÷ | ÷ | division sign | |
| 248 | o | o | o | Latin small letter o with stroke | |
| 249 | ù | ù | ù | Latin small letter u with grave | |
| 250 | ú | ú | ú | Latin small letter u with acute | |
| 251 | ^u | ^u | ^u | Latin small letter with circumflex | |
| 252 | ü | ü | ü | Latin small letter u with diaeresis | |
| 253 | 'y | 'y | 'y | Latin small letter y with acute | |
| 254 | th | th | th | Latin small letter thorn | |
| 255 | "y | "y | "y | Latin small letter y with diaeresis |
3. ASCII 字符集
ASCII 使用 0 到 31（以及 127）之间的值作为控制字符。
ASCII 使用 32 到 126 的值表示字母、数字和符号。
ASCII 不使用 128 到 255 之间的值。
4. ANSI 字符集 (Windows-1252)
对于 0 到 127 的值，ANSI 与 ASCII 相同。
ANSI 有一组专有的字符，其值从 128 到 159。
对于 160 到 255 的值，ANSI 与 UTF-8 相同。
5. ISO-8859-1 字符集
对于 0 到 127 的值，8859-1 与 ASCII 相同。
8859-1 不使用 128 到 159 之间的值。
对于从 160 到 255 的值，8859-1 与 UTF-8 相同。
6. UTF-8 字符集
对于 0 到 127 的值，UTF-8 与 ASCII 相同。
UTF-8 不使用 12 8到 159 之间的值。
对于 160 到 255 之间的值，UTF-8 与 ANSI 和 8859-1 相同。
UTF-8 从值 256 继续，包含超过 10000 个不同字符。
如需深入研究，请阅读我们完整的 HTML 字符集参考手册。
7. @charset CSS 规则
您可以使用 CSS @charset 规则来指定样式表中使用的字符编码：
范例
将样式表的编码设置为 Unicode UTF-8：
@charset "UTF-8";
HTML 统一资源定位器:：URL 也被称为网址。1. URL - Uniform Resource Locator：当您点击 HTML 页面中的某个链接时，对应的 <a> 标签指向万维网上的一个地址。统一资源定位器（URL）用于定位万维网上的文档（或其他数据）。
