良好的XHTML规则

尽管目前浏览器都兼容HTML，但为了使网页符合标准，设计者应该尽量使用XHTML规范来编写代码，在使用中要注意并遵循以下几点规范：

一、以正确的DOCTYPE和名字空间开始

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">  

<html xmlns="http://www.w3.org/1999/xhtml"> 

二、使用META内容元素声明你的内容编码语言

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

三、用小写字母写所有元素和属性名称

四、给所有属性值加引号

五、给所有属性赋一个值

六、关闭所有标签

七、用空格和斜杠关闭空标签

<br />

八、不要在注释内容中使用“--”

九、把所有符号编码化

HTML特殊符号对照表
特殊符号
命名实体
十进制编码
特殊符号
命名实体
十进制编码
Α
&Alpha;
&#913;
Β
&Beta;
&#914;
Γ
&Gamma;
&#915;
Δ
&Delta;
&#916;
Ε
&Epsilon;
&#917;
Ζ
&Zeta;
&#918;
Η
&Eta;
&#919;
Θ
&Theta;
&#920;
Ι
&Iota;
&#921;
Κ
&Kappa;
&#922;
Λ
&Lambda;
&#923;
Μ
&Mu;
&#924;
Ν
&Nu;
&#925;
Ξ
&Xi;
&#926;
Ο
&Omicron;
&#927;
Π
&Pi;
&#928;
Ρ
&Rho;
&#929;
Σ
&Sigma;
&#931;
Τ
&Tau;
&#932;
Υ
&Upsilon;
&#933;
Φ
&Phi;
&#934;
Χ
&Chi;
&#935;
Ψ
&Psi;
&#936;
Ω
&Omega;
&#937;
α
&alpha;
&#945;
β
&beta;
&#946;
γ
&gamma;
&#947;
δ
&delta;
&#948;
ε
&epsilon;
&#949;
ζ
&zeta;
&#950;
η
&eta;
&#951;
θ
&theta;
&#952;
ι
&iota;
&#953;
κ
&kappa;
&#954;
λ
&lambda;
&#955;
μ
&mu;
&#956;
ν
&nu;
&#957;
ξ
&xi;
&#958;
ο
&omicron;
&#959;
π
&pi;
&#960;
ρ
&rho;
&#961;
ς
&sigmaf;
&#962;
σ
&sigma;
&#963;
τ
&tau;
&#964;
υ
&upsilon;
&#965;
φ
&phi;
&#966;
χ
&chi;
&#967;
ψ
&psi;
&#968;
ω
&omega;
&#969;
ϑ
&thetasym;
&#977;
ϒ
&upsih;
&#978;
ϖ
&piv;
&#982;
•
&bull;
&#8226;
…
&hellip;
&#8230;
′
&prime;
&#8242;
″
&Prime;
&#8243;
‾
&oline;
&#8254;
⁄
&frasl;
&#8260;
℘
&weierp;
&#8472;
ℑ
&image;
&#8465;
ℜ
&real;
&#8476;
™
&trade;
&#8482;
ℵ
&alefsym;
&#8501;
←
&larr;
&#8592;
↑
&uarr;
&#8593;
→
&rarr;
&#8594;
↓
&darr;
&#8595;
↔
&harr;
&#8596;
↵
&crarr;
&#8629;
⇐
&lArr;
&#8656;
⇑
&uArr;
&#8657;
⇒
&rArr;
&#8658;
⇓
&dArr;
&#8659;
⇔
&hArr;
&#8660;
∀
&forall;
&#8704;
∂
&part;
&#8706;
∃
&exist;
&#8707;
∅
&empty;
&#8709;
∇
&nabla;
&#8711;
∈
&isin;
&#8712;
∉
&notin;
&#8713;
∋
&ni;
&#8715;
∏
&prod;
&#8719;
∑
&sum;
&#8722;
−
&minus;
&#8722;
∗
&lowast;
&#8727;
√
&radic;
&#8730;
∝
&prop;
&#8733;
∞
&infin;
&#8734;
∠
&ang;
&#8736;
∧
&and;
&#8869;
∨
&or;
&#8870;
∩
&cap;
&#8745;
∪
&cup;
&#8746;
∫
&int;
&#8747;
∴
&there4;
&#8756;
∼
&sim;
&#8764;
≅
&cong;
&#8773;
≈
&asymp;
&#8773;
≠
&ne;
&#8800;
≡
&equiv;
&#8801;
≤
&le;
&#8804;
≥
&ge;
&#8805;
⊂
&sub;
&#8834;
⊃
&sup;
&#8835;
⊄
&nsub;
&#8836;
⊆
&sube;
&#8838;
⊇
&supe;
&#8839;
⊕
&oplus;
&#8853;
⊗
&otimes;
&#8855;
⊥
&perp;
&#8869;
⋅
&sdot;
&#8901;
⌈
&lceil;
&#8968;
⌉
&rceil;
&#8969;
⌊
&lfloor;
&#8970;
⌋
&rfloor;
&#8971;
◊
&loz;
&#9674;
♠
&spades;
&#9824;
♣
&clubs;
&#9827;
♥
&hearts;
&#9829;
♦
&diams;
&#9830;
&nbsp;
&#160;
¡
&iexcl;
&#161;
¢
&cent;
&#162;
£
&pound;
&#163;
¤
&curren;
&#164;
¥
&yen;
&#165;
¦
&brvbar;
&#166;
§
&sect;
&#167;
¨
&uml;
&#168;
©
&copy;
&#169;
ª
&ordf;
&#170;
«
&laquo;
&#171;
¬
&not;
&#172;
­
&shy;
&#173;
®
&reg;
&#174;
¯
&macr;
&#175;
°
&deg;
d&#176;
±
&plusmn;
&#177;
²
&sup2;
&#178;
³
&sup3;
&#179;
´
&acute;
&#180;
µ
&micro;
&#181;
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原文地址：https://www.cnblogs.com/java20130723/p/3211604.html