diff --git a/modules/version/version.go b/modules/version/version.go
index efedb39d..08dca7f4 100644
--- a/modules/version/version.go
+++ b/modules/version/version.go
@@ -20,6 +20,12 @@ var (
 	GitCommit string
 )
 
+func init() {
+	if GitCommit == `` {
+		GitCommit = `HEAD`
+	}
+}
+
 // AddCommands ...
 func AddCommands(rootCmd *cobra.Command) {
 	versionCmd := &cobra.Command{
diff --git a/theme/blog/statics/scripts/header.js b/theme/blog/statics/scripts/header.js
index 91528c32..266ac255 100644
--- a/theme/blog/statics/scripts/header.js
+++ b/theme/blog/statics/scripts/header.js
@@ -104,7 +104,7 @@ TaoBlog.fn.fadeIn = function(elem, callback) {
 	elem.style.display = 'block';
 	if (typeof callback == 'function') {
 		elem.addEventListener('animationend', function(event) {
-			console.log('fade-in animationend');
+			// console.log('fade-in animationend');
 			callback();
 		}, { once: true});
 	}
@@ -113,7 +113,7 @@ TaoBlog.fn.fadeIn = function(elem, callback) {
 TaoBlog.fn.fadeOut = function(elem, callback) {
 	elem.classList.remove('fade-in');
 	elem.addEventListener('animationend', function(event) {
-		console.log('fade-out animationend');
+		// console.log('fade-out animationend');
 		elem.style.display = 'none';
 		if (typeof callback == 'function') {
 			callback();
diff --git a/theme/modules/handle304/handle304.go b/theme/modules/handle304/handle304.go
index 308c5238..d3e80f0b 100644
--- a/theme/modules/handle304/handle304.go
+++ b/theme/modules/handle304/handle304.go
@@ -1,13 +1,14 @@
 package handle304
 
 import (
+	"fmt"
 	"net/http"
 	"time"
 
 	"github.com/movsb/taoblog/modules/version"
 )
 
-const httpgmtFormat = "Mon, 02 Jan 2006 15:04:05 GMT"
+const httpGmtFormat = "Mon, 02 Jan 2006 15:04:05 GMT"
 
 // Requester ...
 type Requester interface {
@@ -19,11 +20,15 @@ type Responder interface {
 	Response(w http.ResponseWriter)
 }
 
-// ArticleRequest ...
+// ArticleRequest 判断是否符合 304 请求。
+// 如果符合，返回 true；否则，返回 false。
 func ArticleRequest(w http.ResponseWriter, req *http.Request, modified time.Time) bool {
 	handlers := []Requester{
 		NotModified{modified},
-		CommitMatch{},
+		EntityTag{
+			modified: modified,
+			version:  version.GitCommit,
+		},
 	}
 	for _, handler := range handlers {
 		if !handler.Request(req) {
@@ -38,7 +43,10 @@ func ArticleRequest(w http.ResponseWriter, req *http.Request, modified time.Time
 func ArticleResponse(w http.ResponseWriter, modified time.Time) {
 	handlers := []Responder{
 		NotModified{modified},
-		CommitMatch{},
+		EntityTag{
+			modified: modified,
+			version:  version.GitCommit,
+		},
 	}
 	for _, handler := range handlers {
 		handler.Response(w)
@@ -53,40 +61,34 @@ type NotModified struct {
 // Request ...
 func (nm NotModified) Request(req *http.Request) bool {
 	h := req.Header.Get(`If-Modified-Since`)
-	t, _ := time.ParseInLocation(httpgmtFormat, h, time.UTC)
+	t, _ := time.ParseInLocation(httpGmtFormat, h, time.UTC)
 	return t.Equal(nm.Modified)
 }
 
 // Response ...
 func (nm NotModified) Response(w http.ResponseWriter) {
-	w.Header().Add(`Last-Modified`, nm.Modified.UTC().Format(httpgmtFormat))
+	w.Header().Add(`Last-Modified`, nm.Modified.UTC().Format(httpGmtFormat))
 }
 
-// CommitMatch ...
-type CommitMatch struct {
+// 格式：文章的修改日期-博客版本号
+// Typically, the ETag value is a hash of the content, a hash of the last modification timestamp, or just a revision number.
+// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag
+type EntityTag struct {
+	modified time.Time
+	version  string
+}
+
+func (cm EntityTag) format() string {
+	return fmt.Sprintf(`"%d-%s"`, cm.modified.Unix(), cm.version)
 }
 
 // Request ...
-func (cm CommitMatch) Request(req *http.Request) bool {
-	commitCookie, err := req.Cookie(`commit`)
-	if err != nil {
-		return false
-	}
-	return commitCookie.Value == version.GitCommit
+func (cm EntityTag) Request(req *http.Request) bool {
+	haystack := req.Header.Get(`If-None-Match`)
+	return haystack == cm.format()
 }
 
 // Response ...
-func (cm CommitMatch) Response(w http.ResponseWriter) {
-	v := version.GitCommit
-	if v == `` {
-		v = `HEAD`
-	}
-	http.SetCookie(w, &http.Cookie{
-		Name:     `commit`,
-		Value:    v,
-		Path:     `/`,
-		MaxAge:   0,
-		Secure:   false,
-		HttpOnly: true,
-	})
+func (cm EntityTag) Response(w http.ResponseWriter) {
+	w.Header().Add(`ETag`, cm.format())
 }