diff --git a/notes/comment.go b/notes/comment.go
new file mode 100755
index 0000000..5e6d88a
--- /dev/null
+++ b/notes/comment.go
@@ -0,0 +1,61 @@
+package notes
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"local/notes-server/filetree"
+	"os"
+	"path"
+	"strings"
+)
+
+func (n *Notes) Comment(urlPath string, lineno int, comment string) error {
+	p := filetree.NewPathFromURL(urlPath)
+	if stat, err := os.Stat(p.Local); err != nil {
+		return errors.New("cannot comment as it does not exist")
+	} else if stat.IsDir() {
+		return errors.New("cannot comment on a dir")
+	}
+	f, err := os.Open(p.Local)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	f2, err := ioutil.TempFile(os.TempDir(), path.Base(p.Local)+".*")
+	if err != nil {
+		return err
+	}
+	defer f2.Close()
+	reader := bufio.NewReader(f)
+	writer := io.Writer(f2)
+	for i := 0; i < lineno+1; i++ {
+		line, _, err := reader.ReadLine()
+		if err != nil {
+			return err
+		}
+		_, err = io.Copy(writer, bytes.NewReader(line))
+		if err != nil {
+			return err
+		}
+		_, err = writer.Write([]byte("\n"))
+		if err != nil {
+			return err
+		}
+	}
+	formatted := "\n"
+	formatted += fmt.Sprintf("> *%s*\n", comment)
+	_, err = io.Copy(writer, strings.NewReader(formatted))
+	if err != nil {
+		return err
+	}
+	_, err = io.Copy(writer, reader)
+	if err != nil {
+		return err
+	}
+	f2.Close()
+	return os.Rename(f2.Name(), p.Local)
+}
diff --git a/notes/comment_test.go b/notes/comment_test.go
new file mode 100644
index 0000000..db80125
--- /dev/null
+++ b/notes/comment_test.go
@@ -0,0 +1,56 @@
+package notes
+
+import (
+	"bytes"
+	"io/ioutil"
+	"local/notes-server/config"
+	"os"
+	"path"
+	"strings"
+	"testing"
+)
+
+func TestComment(t *testing.T) {
+	d, err := ioutil.TempDir(os.TempDir(), "testComment.*")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(d)
+	f, err := ioutil.TempFile(d, "testFile.*")
+	if err != nil {
+		t.Fatal(err)
+	}
+	f.Write([]byte(`
+   hello
+   world
+   # i have a heading
+   ## i have a subber heading
+   ### i have a[heading with](http://google.com) a hyperlink
+   ## *I think this heading is in italics*
+   `))
+	f.Close()
+	fpath := path.Join("/comment", strings.TrimPrefix(f.Name(), d))
+	config.Root = d
+	n := &Notes{}
+	t.Logf("d=%s, fpath=%s", d, fpath)
+
+	if err := n.Comment("/comment/a", 5, "a"); err == nil {
+		t.Error(err)
+	}
+
+	if err := n.Comment(fpath, -1, "illegal line no"); err != nil {
+		t.Error(err)
+	}
+
+	if err := n.Comment(fpath, 10000, "big line no"); err == nil {
+		t.Error(err)
+	}
+
+	if err := n.Comment(fpath, 0, "first_line_OK"); err != nil {
+		t.Error(err)
+	} else if b, err := ioutil.ReadFile(f.Name()); err != nil {
+		t.Error(err)
+	} else if !bytes.Contains(b, []byte("> *first_line_OK*\n")) {
+		t.Errorf("%s", b)
+	}
+}
diff --git a/notes/file.go b/notes/file.go
index 63fc8b8..adc52e0 100755
--- a/notes/file.go
+++ b/notes/file.go
@@ -1,12 +1,16 @@
 package notes
 
 import (
+	"bytes"
 	"encoding/base64"
 	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
 	"local/notes-server/filetree"
+	"log"
+	"path"
+	"regexp"
 	"strings"
 
 	"github.com/gomarkdown/markdown"
@@ -23,15 +27,57 @@ func (n *Notes) File(urlPath string) (string, error) {
 	b, _ := ioutil.ReadFile(p.Local)
 	renderer := html.NewRenderer(html.RendererOptions{
 		Flags:          html.CommonFlags | html.TOC,
-		RenderNodeHook: n.commentFormer(),
+		RenderNodeHook: n.commentFormer(urlPath, b),
 	})
 	parser := parser.NewWithExtensions(parser.CommonExtensions | parser.HeadingIDs | parser.AutoHeadingIDs | parser.Titleblock)
 	content := markdown.ToHTML(b, parser, renderer)
 	return string(content) + "\n", nil
 }
 
-func (n *Notes) commentFormer() html.RenderNodeFunc {
-	header_n := 0
+func (n *Notes) commentFormer(urlPath string, md []byte) html.RenderNodeFunc {
+	urlPath = strings.TrimPrefix(urlPath, "/")
+	urlPath = strings.TrimPrefix(urlPath, strings.Split(urlPath, "/")[0])
+	lines := bytes.Split(md, []byte("\n"))
+	cur := -1
+	nextHeader := func() {
+		cur++
+		for cur < len(lines) {
+			if bytes.Contains(lines[cur], []byte("```")) {
+				cur++
+				for cur < len(lines) && !bytes.Contains(lines[cur], []byte("```")) {
+					cur++
+				}
+				cur++
+			}
+			if cur >= len(lines) {
+				break
+			}
+			line := lines[cur]
+			if ok, err := regexp.Match(`^\s*#+\s*[^\s]+\s*$`, line); err != nil {
+				panic(err)
+			} else if ok {
+				return
+			}
+			cur++
+		}
+	}
+	return func(w io.Writer, node ast.Node, entering bool) (ast.WalkStatus, bool) {
+		if heading, ok := node.(*ast.Heading); ok && !entering {
+			log.Printf("%+v", heading)
+			nextHeader()
+			fmt.Fprintf(w, `
+            <form method="POST" action=%q class="comment">
+               <input name="lineno" type="number" style="display:none" value="%d"/>
+               <input autocomplete="off" name="content" type="text"/>
+               <input type="submit"/>
+            </form>
+         `, path.Join("/comment", urlPath)+"#"+heading.HeadingID, cur)
+		}
+		return ast.GoToNext, false
+	}
+}
+
+func (n *Notes) commentFormerOld() html.RenderNodeFunc {
 	return func(w io.Writer, node ast.Node, entering bool) (ast.WalkStatus, bool) {
 		if heading, ok := node.(*ast.Heading); ok {
 			if !entering {
diff --git a/server/comment.go b/server/comment.go
new file mode 100755
index 0000000..e2797ba
--- /dev/null
+++ b/server/comment.go
@@ -0,0 +1,37 @@
+package server
+
+import (
+	"html"
+	"local/notes-server/filetree"
+	"log"
+	"net/http"
+	"path"
+	"strconv"
+	"strings"
+)
+
+func (s *Server) comment(w http.ResponseWriter, r *http.Request) {
+	log.Println("COMMAND", r.Method, r.FormValue("lineno"), r.FormValue("content"))
+	if r.Method != "POST" {
+		http.NotFound(w, r)
+		return
+	}
+	linenos := r.FormValue("lineno")
+	lineno, err := strconv.Atoi(linenos)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+	comment := r.FormValue("content")
+	comment = html.UnescapeString(comment)
+	comment = strings.ReplaceAll(comment, "\r", "")
+
+	err = s.Notes.Comment(r.URL.Path, lineno, comment)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	url := *r.URL
+	url.Path = path.Join("/notes/", filetree.NewPathFromURL(r.URL.Path).BaseHREF)
+	http.Redirect(w, r, url.String(), http.StatusSeeOther)
+}
diff --git a/server/routes.go b/server/routes.go
index 2e9a3f0..6663dd4 100755
--- a/server/routes.go
+++ b/server/routes.go
@@ -33,6 +33,9 @@ func (s *Server) Routes() error {
 		fmt.Sprintf("create/%s%s", wildcard, wildcard): {
 			handler: s.gzip(s.authenticate(s.create)),
 		},
+		fmt.Sprintf("comment/%s%s", wildcard, wildcard): {
+			handler: s.gzip(s.authenticate(s.comment)),
+		},
 		fmt.Sprintf("search"): {
 			handler: s.gzip(s.authenticate(s.search)),
 		},