diff --git a/edit.html b/edit.html
index 08960f0c..d5473844 100644
--- a/edit.html
+++ b/edit.html
@@ -61,11 +61,16 @@
 			.aligned {
 				display: table-row;
 			}
-			.aligned > * {
+			.aligned > *:not(img) {
 				display: table-cell;
 				margin-top: 0.1rem;
 				min-height: 1.4rem;
 			}
+			img[src="help.png"] {
+				cursor: pointer;
+				vertical-align: middle;
+				margin-left: 0.2rem;
+			}
 			input[type="checkbox"] {
 				margin-left: 0.1rem;
 			}
@@ -88,11 +93,6 @@
 				margin-right: 0.5rem;
 				margin-bottom: 0.5rem;
 			}
-			#actions img {
-				margin-left: 0.2rem;
-				position: relative;
-				top: 0.2rem;
-			}
 			/* options */
 			#options [type="number"] {
 				max-width: 2.5rem;
@@ -202,6 +202,55 @@
 			.applies-to img {
 				vertical-align: bottom;
 			}
+			/************ help popup ************/
+			#help-popup {
+				top: 3rem;
+				right: 3rem;
+				max-width: 50vw;
+				position: fixed;
+				display: none;
+				background-color: white;
+				box-shadow: 3px 3px 30px rgba(0, 0, 0, 0.5);
+				padding: 0.5rem;
+				z-index: 9999;
+			}
+			#help-popup .title {
+				font-weight: bold;
+				background-color: rgba(0,0,0,0.05);
+				margin: -0.5rem -0.5rem 0.5rem;
+				padding: 0.5rem;
+			}
+			#help-popup .contents {
+				max-height: calc(100vh - 8rem);
+				overflow-y: auto;
+			}
+			#help-popup .close-icon {
+				cursor: pointer;
+				width: 8px;
+				height: 8px;
+				position: absolute;
+				right: 0.5rem;
+				top: 0.75rem;
+				background: linear-gradient(-45deg, transparent 5px, black 5px, black 6px, transparent 6.5px), linear-gradient(45deg, transparent 5px, black 5px, black 6px, transparent 6.5px);
+			}
+
+			.keymap-list {
+				font-size: 85%;
+				line-height: 1.0;
+				border-spacing: 0;
+				word-break: break-all;
+			}
+			.keymap-list input {
+				width: 100%;
+			}
+			.keymap-list tr:nth-child(odd) {
+				background-color: rgba(0, 0, 0, 0.07);
+			}
+			.keymap-list td:first-child {
+				white-space: nowrap;
+				font-family: monospace;
+				padding-right: 0.5rem;
+			}
 
 			/************ reponsive layouts ************/
 			@media(max-width:737px) {
@@ -248,7 +297,7 @@
 				#options {
 					-webkit-column-count: 2;
 				}
-				#options .aligned > * {
+				#options .aligned > *:not(img) {
 					margin: 1px 0 0 0; /* workaround the flowing-padding column bug in webkit */
 					padding-right: 0.4rem;
 					vertical-align: baseline;
@@ -336,6 +385,7 @@
 				<div class="option aligned">
 					<label id="keyMap-label" for="editor.keyMap" i18n-text="cm_keyMap"></label>
 					<select data-option="keyMap" id="editor.keyMap"></select>
+					<img id="keyMap-help" src="help.png" i18n-alt="helpAlt">
 				</div>
 				<div class="option aligned">
 					<label id="theme-label" for="editor.theme" i18n-text="cm_theme"></label>
@@ -346,5 +396,9 @@
 		<section id="sections">
 			<h2><span id="sections-heading" i18n-text="styleSectionsTitle"></span><img id="sections-help" src="help.png" i18n-alt="helpAlt"></h2>
 		</section>
+		<div id="help-popup">
+			<div class="title"></div><div class="close-icon"></div>
+			<div class="contents"></div>
+		</div>
 	</body>
 </html>
diff --git a/edit.js b/edit.js
index cf3cc63a..63488d60 100644
--- a/edit.js
+++ b/edit.js
@@ -703,6 +703,7 @@ function initHooks() {
 	document.getElementById("to-mozilla-help").addEventListener("click", showToMozillaHelp, false);
 	document.getElementById("save-button").addEventListener("click", save, false);
 	document.getElementById("sections-help").addEventListener("click", showSectionHelp, false);
+	document.getElementById("keyMap-help").addEventListener("click", showKeyMapHelp, false);
 
 	setupGlobalSearch();
 	setCleanGlobal();
@@ -835,19 +836,90 @@ function toMozillaFormat() {
 }
 
 function showSectionHelp() {
-	showHelp(t("sectionHelp"));
+	showHelp(t("styleSectionsTitle"), t("sectionHelp"));
 }
 
 function showAppliesToHelp() {
-	showHelp(t("appliesHelp"));
+	showHelp(t("appliesLabel"), t("appliesHelp"));
 }
 
 function showToMozillaHelp() {
-	showHelp(t("styleToMozillaFormatHelp"));
+	showHelp(t("styleToMozillaFormat"), t("styleToMozillaFormatHelp"));
 }
 
-function showHelp(text) {
-	alert(text);
+function showKeyMapHelp() {
+	var keyMap = mergeKeyMaps({}, prefs.getPref("editor.keyMap"), CodeMirror.defaults.extraKeys);
+	var keyMapSorted = Object.keys(keyMap)
+		.map(function(key) { return {key: key, cmd: keyMap[key]} })
+		.sort(function(a, b) { return a.cmd < b.cmd || (a.cmd == b.cmd && a.key < b.key) ? -1 : 1 });
+	showHelp(t("cm_keyMap") + ": " + prefs.getPref("editor.keyMap"),
+		'<table class="keymap-list">' +
+			"<thead><tr><th><input></th><th><input></th></tr></thead>" +
+			"<tbody>" + keyMapSorted.map(function(value) {
+				return "<tr><td>" + value.key + "</td><td>" + value.cmd + "</td></tr>";
+			}).join("") +
+			"</tbody>" +
+		"</table>");
+	document.querySelector("#help-popup table").addEventListener("input", function(event) {
+		var input = event.target;
+		var query = new RegExp(input.value.replace(/([{}()\[\]\/\\.+?^$:=*!|])/g, "\\$1"), "gi");
+		var col = input.parentNode.cellIndex;
+		this.tBodies[0].childNodes.forEach(function(row) {
+			var cell = row.children[col];
+			if (query.test(cell.textContent)) {
+				row.style.display = "";
+				cell.innerHTML = cell.textContent.replace(query, "<mark>$&</mark>");
+			} else {
+				row.style.display = "none";
+			}
+		});
+	});
+
+	function mergeKeyMaps(merged) {
+		[].slice.call(arguments, 1).forEach(function(keyMap) {
+			if (typeof keyMap == "string") {
+				keyMap = CodeMirror.keyMap[keyMap];
+			}
+			Object.keys(keyMap).forEach(function(key) {
+				var cmd = keyMap[key];
+				// filter out '...', 'attach', etc. (hotkeys start with an uppercase letter)
+				if (!merged[key] && !key.match(/^[a-z]/) && cmd != "...") {
+					if (typeof cmd == "function") {
+						// for 'emacs' keymap: provide at least something meaningful (hotkeys and the function body)
+						// for 'vim*' keymaps: almost nothing as it doesn't rely on CM keymap mechanism
+						cmd = cmd.toString().replace(/^function.*?\{[\s\r\n]*([\s\S]+?)[\s\r\n]*\}$/, "$1");
+						merged[key] = cmd.length <= 200 ? cmd : cmd.substr(0, 200) + "...";
+					} else {
+						merged[key] = cmd;
+					}
+				}
+			});
+			if (keyMap.fallthrough) {
+				merged = mergeKeyMaps(merged, keyMap.fallthrough);
+			}
+		});
+		return merged;
+	}
+}
+
+function showHelp(title, text) {
+	var div = document.getElementById("help-popup");
+	div.querySelector(".contents").innerHTML = text;
+	div.querySelector(".title").innerHTML = title;
+
+	if (getComputedStyle(div).display == "none") {
+		document.addEventListener("keydown", closeHelp);
+		div.querySelector(".close-icon").onclick = closeHelp; // avoid chaining on multiple showHelp() calls
+	}
+
+	div.style.display = "block";
+
+	function closeHelp(e) {
+		if (e.type == "click" || (e.keyCode == 27 && !e.altKey && !e.ctrlKey && !e.shiftKey && !e.metaKey)) {
+			div.style.display = "";
+			document.removeEventListener("keydown", closeHelp);
+		}
+	}
 }
 
 function getParams() {