Clear all output is implemented.

IPython/frontend/html/notebook/static/js/notebook.js

@@ -443,7 +443,7 b' var IPython = (function (IPython) {'
     };
 
 
-    // Cell collapsing
+    // Cell collapsing and output clearing
 
     Notebook.prototype.collapse = function (index) {
         var i = this.index_or_selected(index);
@@ -465,6 +465,18 b' var IPython = (function (IPython) {'
         };
     };
 
+
+    Notebook.prototype.clear_all_output = function () {
+        var ncells = this.ncells();
+        var cells = this.cells();
+        for (var i=0; i<ncells; i++) {
+            if (cells[i] instanceof IPython.CodeCell) {
+                cells[i].clear_output();
+            }
+        };
+    };
+
+
     // Kernel related things
 
     Notebook.prototype.start_kernel = function () {

IPython/frontend/html/notebook/static/js/panelsection.js

@@ -137,6 +137,9 b' var IPython = (function (IPython) {'
         this.content.find('#expand_cell').click(function () {
             IPython.notebook.expand();
         });
+        this.content.find('#clear_all_output').click(function () {
+            IPython.notebook.clear_all_output();
+        });
         this.content.find('#delete_cell').click(function () {
             IPython.notebook.delete_cell();
         });

IPython/frontend/html/notebook/templates/notebook.html

@@ -89,7 +89,15 b''
                         <button id="to_html">HTML</button>
                         <button id="to_markdown">Markdown</button>
                     </span>
-                    <!-- <span class="button_label">Format</span> -->
+                     <span class="button_label">Format</span> 
+                </div>
+                <div class="section_row">
+                    <span id="toggle_output" class="section_row_buttons">
+                        <button id="collapse_cell">Collapse</button>
+                        <button id="expand_cell">Expand</button>
+                        <button id="clear_all_output">Clear All</button>
+                    </span>
+                    <span class="button_label">Output</span>
                 </div>
                 <div class="section_row">
                     <span id="insert" class="section_row_buttons">
@@ -106,13 +114,6 b''
                     <span class="button_label">Move</span>
                 </div>
                 <div class="section_row">
-                    <span id="toggle_output" class="section_row_buttons">
-                        <button id="collapse_cell">Collapse</button>
-                        <button id="expand_cell">Expand</button>
-                    </span>
-                    <span class="button_label">Output</span>
-                </div>
-                <div class="section_row">
                     <span id="run_cells" class="section_row_buttons">
                         <button id="run_selected_cell">Selected</button>
                         <button id="run_all_cells">All</button>