diff --git a/dist/antd-1.0.4b.tar.gz b/dist/antd-1.0.4b.tar.gz
index dbf02c8..0cfed59 100644
Binary files a/dist/antd-1.0.4b.tar.gz and b/dist/antd-1.0.4b.tar.gz differ
diff --git a/http_server.c b/http_server.c
index 7e9570b..d371df3 100644
--- a/http_server.c
+++ b/http_server.c
@@ -39,6 +39,9 @@ void error_log(const char* fmt, ...)
     	va_end(arguments); 
     	if ((data = (char*)malloc(dlen*sizeof(char))) != 0)
     	{
+			char buf[64];
+			server_time(buf,64);
+			fwrite(buf,strlen(buf),1,server_config.errorfp);
 			va_start(arguments, fmt);
 			vsnprintf(data, dlen, fmt, arguments);
 			va_end(arguments);
@@ -62,6 +65,9 @@ void server_log(const char* fmt, ...)
     	va_end(arguments); 
     	if ((data = (char*)malloc(dlen*sizeof(char))) != 0)
     	{
+			char buf[64];
+			server_time(buf,64);
+			fwrite(buf,strlen(buf),1,server_config.logfp);
 			va_start(arguments, fmt);
 			vsnprintf(data, dlen, fmt, arguments);
 			va_end(arguments);
@@ -670,10 +676,7 @@ void *serve_file(void *data)
 	task->priority++;
 	char *path = (char *)dvalue(rq->request, "ABS_RESOURCE_PATH");
 	char *mime_type = (char *)dvalue(rq->request, "RESOURCE_MIME");
-	// find content length
-	/*if (is_bin(path))
-		__fb(rq->client, path);
-	else*/
+
 	struct stat st;
 	int s = stat(path, &st);
 	
@@ -683,19 +686,43 @@ void *serve_file(void *data)
 	}
 	else
 	{
-		int size = (int)st.st_size;
-		char ibuf[20];
-    	snprintf (ibuf, sizeof(ibuf), "%d",size);
-		antd_response_header_t rhd;
-		rhd.cookie = NULL;
-		rhd.status = 200;
-		rhd.header = dict();
-		dput(rhd.header, "Content-Type", strdup(mime_type));
-		if(!compressable(mime_type) || rq->client->z_level == ANTD_CNONE)
-			dput(rhd.header, "Content-Length", strdup(ibuf));
-		antd_send_header(rq->client, &rhd);
+		// check if it is modified
+		dictionary_t header = (dictionary_t)dvalue(rq->request, "REQUEST_HEADER");
+		char * last_modif_since = (char*)dvalue(header, "If-Modified-Since");
+		time_t t = st.st_ctime;
+		struct tm tm;
+		if(last_modif_since)
+		{
+			strptime(last_modif_since, "%a, %d %b %Y %H:%M:%S GMT", &tm);
+			t = timegm(&tm);
+			//t = mktime(localtime(&t));
+		}
 
-		__f(rq->client, path);
+		if(last_modif_since && st.st_ctime == t)
+		{
+			// return the not changed
+			antd_error(rq->client,304, "");
+		}
+		else
+		{
+			int size = (int)st.st_size;
+			char ibuf[64];
+			snprintf (ibuf, sizeof(ibuf), "%d",size);
+			antd_response_header_t rhd;
+			rhd.cookie = NULL;
+			rhd.status = 200;
+			rhd.header = dict();
+			dput(rhd.header, "Content-Type", strdup(mime_type));
+			if(!compressable(mime_type) || rq->client->z_level == ANTD_CNONE)
+				dput(rhd.header, "Content-Length", strdup(ibuf));
+			gmtime_r(&st.st_ctime, &tm);
+			strftime(ibuf, 255, "%a, %d %b %Y %H:%M:%S GMT", &tm);
+			dput(rhd.header, "Last-Modified", strdup(ibuf));
+			dput(rhd.header, "Cache-Control", strdup("no-cache"));
+			antd_send_header(rq->client, &rhd);
+
+			__f(rq->client, path);
+		}
 	}
 	
 	return task;
diff --git a/lib/utils.c b/lib/utils.c
index 4f02754..377b4b8 100644
--- a/lib/utils.c
+++ b/lib/utils.c
@@ -85,19 +85,26 @@ void removeAll(const char* path,int mode)
 	
 }
 
-char* __time(time_t time)
-{
-	struct tm *t = localtime(&time);
-	char * buf = asctime(t);
-	char* pos = strchr(buf,'\n');
-	if(pos) *pos = '\0';
-	return buf;
-}
-char* server_time()
-{
-	return __time(time(NULL));
-}
+// WARNING:
+// TODO: remove it, this function is not thread-safe
 
+void timestr(time_t time, char* buf,int len,char* format, int gmt)
+{
+	struct tm t;
+    if(gmt)
+    {
+        gmtime_r(&time, &t);
+    }
+    else
+    {
+        localtime_r(&time, &t);
+    }
+	strftime(buf, len, format, &t);
+}
+void server_time(char* buf, int len)
+{
+	timestr(time(NULL), buf, len ,"%a, %d %b %Y %H:%M:%S", 0);
+}
 /**
  * Get extension of a file name
  * @param  file The file name
diff --git a/lib/utils.h b/lib/utils.h
index b92bb40..f475b97 100644
--- a/lib/utils.h
+++ b/lib/utils.h
@@ -56,12 +56,12 @@ THE SOFTWARE.
 #define false 0
 
 #ifdef DEBUG
-	#define LOG(a,...) server_log("%s: [%s: %d]: " a "\n",server_time(), __FILE__, \
+	#define LOG(a,...) server_log(": [%s: %d]: " a "\n", __FILE__, \
 		__LINE__, ##__VA_ARGS__)
 #else
     #define LOG(a,...) do{}while(0)
 #endif
-#define ERROR(a,...) error_log("%s: [%s: %d]: " a "\n", server_time() , __FILE__, \
+#define ERROR(a,...) error_log(": [%s: %d]: " a "\n", __FILE__, \
 		__LINE__, ##__VA_ARGS__)
 // add this to the utils
 #define UNUSED(x) (void)(x)
@@ -83,8 +83,8 @@ dictionary_t __attribute__((weak)) mimes_list();
 char* __s(const char*,...);
 void trim(char*,const char);
 void removeAll(const char* path,int mode);
-char* __time(time_t time);
-char* server_time();
+void timestr(time_t time, char* buf,int len,char* format, int gmt);
+void server_time(char* , int );
 char* ext(const char*);
 char* mime(const char*);
 int match_int(const char*);