html/template: fix broken links

Fixes #7562.

LGTM=nigeltao
R=nigeltao
CC=golang-codereviews
https://golang.org/cl/81190044

src/pkg/html/template/attr.go

@@ -90,7 +90,7 @@ var attrTypeMap = map[string]contentType{
 	"name":            contentTypePlain,
 	"novalidate":      contentTypeUnsafe,
 	// Skip handler names from
-	// http://www.w3.org/TR/html5/Overview.html#event-handlers-on-elements-document-objects-and-window-objects
+	// http://www.w3.org/TR/html5/webappapis.html#event-handlers-on-elements,-document-objects,-and-window-objects
 	// since we have special handling in attrType.
 	"open":        contentTypePlain,
 	"optimum":     contentTypePlain,
@@ -160,7 +160,7 @@ func attrType(name string) contentType {
 
 	// Heuristics to prevent "javascript:..." injection in custom
 	// data attributes and custom attributes like g:tweetUrl.
-	// http://www.w3.org/TR/html5/elements.html#embedding-custom-non-visible-data-with-the-data-attributes:
+	// http://www.w3.org/TR/html5/dom.html#embedding-custom-non-visible-data-with-the-data-*-attributes
 	// "Custom data attributes are intended to store custom data
 	//  private to the page or application, for which there are no
 	//  more appropriate attributes or elements."

src/pkg/html/template/content.go

@@ -16,7 +16,8 @@ type (
 	//   2. The CSS3 rule production, such as `a[href=~"https:"].foo#bar`.
 	//   3. CSS3 declaration productions, such as `color: red; margin: 2px`.
 	//   4. The CSS3 value production, such as `rgba(0, 0, 255, 127)`.
-	// See http://www.w3.org/TR/css3-syntax/#style
+	// See http://www.w3.org/TR/css3-syntax/#parsing and
+	// https://web.archive.org/web/20090211114933/http://w3.org/TR/css3-syntax#style
 	CSS string
 
 	// HTML encapsulates a known safe HTML document fragment.

src/pkg/html/template/context.go

@@ -13,7 +13,7 @@ import (
 //
 // The zero value of type context is the start context for a template that
 // produces an HTML fragment as defined at
-// http://www.w3.org/TR/html5/the-end.html#parsing-html-fragments
+// http://www.w3.org/TR/html5/syntax.html#the-end
 // where the context element is null.
 type context struct {
 	state   state
@@ -96,7 +96,7 @@ const (
 	// stateHTMLCmt occurs inside an <!-- HTML comment -->.
 	stateHTMLCmt
 	// stateRCDATA occurs inside an RCDATA element (<textarea> or <title>)
-	// as described at http://dev.w3.org/html5/spec/syntax.html#elements-0
+	// as described at http://www.w3.org/TR/html5/syntax.html#elements-0
 	stateRCDATA
 	// stateAttr occurs inside an HTML attribute whose content is text.
 	stateAttr

src/pkg/html/template/escape.go

@@ -664,7 +664,7 @@ func contextAfterText(c context, s []byte) (context, int) {
 		i = len(s)
 	}
 	if c.delim == delimSpaceOrTagEnd {
-		// http://www.w3.org/TR/html5/tokenization.html#attribute-value-unquoted-state
+		// http://www.w3.org/TR/html5/syntax.html#attribute-value-(unquoted)-state
 		// lists the runes below as error characters.
 		// Error out because HTML parsers may differ on whether
 		// "<a id= onclick=f("     ends inside id's or onclick's value,

src/pkg/html/template/html.go

@@ -50,12 +50,12 @@ func htmlEscaper(args ...interface{}) string {
 // htmlReplacementTable contains the runes that need to be escaped
 // inside a quoted attribute value or in a text node.
 var htmlReplacementTable = []string{
-	// http://www.w3.org/TR/html5/tokenization.html#attribute-value-unquoted-state: "
+	// http://www.w3.org/TR/html5/syntax.html#attribute-value-(unquoted)-state
 	// U+0000 NULL Parse error. Append a U+FFFD REPLACEMENT
 	// CHARACTER character to the current attribute's value.
 	// "
 	// and similarly
-	// http://www.w3.org/TR/html5/tokenization.html#before-attribute-value-state
+	// http://www.w3.org/TR/html5/syntax.html#before-attribute-value-state
 	0:    "\uFFFD",
 	'"':  """,
 	'&':  "&",