Adding minor help strings for keyboard shortcuts.

IPython/frontend/html/notebook/static/css/notebook.css

@@ -83,6 +83,17 b' span.section_row_buttons > button {'
     float: right;
 }
 
+.help_string {
+    float: right;
+    width: 170px;
+    padding: 0px 5px;
+    text-align: center;
+}
+
+.help_string_label {
+    float: right;
+}
+
 #autoindent_span {
     float: right;
 }

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

@@ -165,6 +165,14 b''
                         <button id="sympy_help"><a href="http://docs.sympy.org/dev/index.html" target="_blank">SymPy</a></button>
                     </span>
                 </div>
+                <div class="section_row">
+                    <span class="help_string">run selected cell</span>
+                    <span class="help_string_label">Shift-Enter |</span>
+                </div>
+                <div class="section_row">
+                    <span class="help_string">run in terminal mode</span>
+                    <span class="help_string_label">Ctrl-Enter  |</span>
+                </div>
             </div>
         </div>