are leading and trailing whitespaces ignored in html?
问题 html4 says this: In order to avoid problems with SGML line break rules and inconsistencies among extant implementations, authors should not rely on user agents to render white space immediately after a start tag or immediately before an end tag. Thus, authors, and in particular authoring tools, should write: <P>We offer free <A>technical support</A> for subscribers.</P> and not: <P>We offer free<A> technical support </A>for subscribers.</P> and this: SGML (see [ISO8879], section 7.6.1)