26个字母，系统已用7个
系统已用： a, b, i, p, q, s, u
可用自定义标签：c, d, e, f, g, h, j, k, l, m, n, o, r, t, v, w, x, y, z
<a>a</a> function HTMLAnchorElement() { [native code] }
<p>p</p> function HTMLParagraphElement() { [native code] }
<q>q</q> function HTMLQuoteElement() { [native code] }
<b>b</b> function HTMLElement() { [native code] }
<i>i</i> function HTMLElement() { [native code] }
<s>s</s> function HTMLElement() { [native code] }
<u>u</u> function HTMLElement() { [native code] }
===========================================================
<c>c</c> function HTMLUnknownElement() { [native code] }
<d>d</d> function HTMLUnknownElement() { [native code] }
<e>e</e> function HTMLUnknownElement() { [native code] }
<f>f</f> function HTMLUnknownElement() { [native code] }
<g>g</g> function HTMLUnknownElement() { [native code] }
<h>h</h> function HTMLUnknownElement() { [native code] }
<j>j</j> function HTMLUnknownElement() { [native code] }
<k>k</k> function HTMLUnknownElement() { [native code] }
<l>l</l> function HTMLUnknownElement() { [native code] }
<m>m</m> function HTMLUnknownElement() { [native code] }
<n>n</n> function HTMLUnknownElement() { [native code] }
<o>o</o> function HTMLUnknownElement() { [native code] }
<r>r</r> function HTMLUnknownElement() { [native code] }
<t>t</t> function HTMLUnknownElement() { [native code] }
<v>v</v> function HTMLUnknownElement() { [native code] }
<w>w</w> function HTMLUnknownElement() { [native code] }
<x>x</x> function HTMLUnknownElement() { [native code] }
<y>y</y> function HTMLUnknownElement() { [native code] }
<z>z</z> function HTMLUnknownElement() { [native code] }