diff --git a/index.js b/index.js
index dd9010b..55b5637 100644
--- a/index.js
+++ b/index.js
@@ -18,6 +18,8 @@ var QCore = function() {
   this.index_parts = [];
   this.last_part = { start: 0, end: 0 };
 
+  this.etags = {}; // etags cache, obj: uri { etag: '...', timestamp: }
+
   this.res_cache = {}; // resource cache ('/view.png' => '03xc345');
   this.rules = {};
 
@@ -428,17 +430,29 @@ qwiki.act('', function(req, res) {
     var path = 'wiki/'+req.url;
     fs.stat(path, function(err, stat) {
       if (err == null) {
-        res.writeHead(200, "OK", {
-          "Content-Type": mimetype,
-          "Content-Length": stat.size
-        });
-        var rs = fs.createReadStream(path);
-        rs.on('data', function(chunk) {
-          res.write(chunk);
-        });
-        rs.on('end', function() {
+        // TODO: etags should actually be based on binary data(CRC32, etc.), not last modified
+        // TODO: files should not be stat()`d each call, but should be cached and updated when the file updates (how? browser-based upload interface?)
+        var mtime = stat.mtime.getTime();
+        if (!(path in qwiki.etags) || qwiki.etags[path] != mtime) {
+          qwiki.etags[path] = mtime;
+        }
+        if ('if-none-match' in req.headers && req.headers['if-none-match'] == qwiki.etags[path]) {
+          res.writeHead(304, "Not Modified");
           res.end();
-        });
+        } else {
+          res.writeHead(200, "OK", {
+            "Content-Type": mimetype,
+            "Content-Length": stat.size,
+            "ETag": mtime
+          });
+          var rs = fs.createReadStream(path);
+          rs.on('data', function(chunk) {
+            res.write(chunk);
+          });
+          rs.on('end', function() {
+            res.end();
+          });
+        }
       } else if (err.code == 'ENOENT') {
         res.writeHead(404);
         res.end();