diff --git a/extensions/html/client/src/htmlMain.ts b/extensions/html/client/src/htmlMain.ts
index db3d12b2f3a..15911915194 100644
--- a/extensions/html/client/src/htmlMain.ts
+++ b/extensions/html/client/src/htmlMain.ts
@@ -32,7 +32,7 @@ export function activate(context: ExtensionContext) {
 	let toDispose = context.subscriptions;
 
 	let packageInfo = getPackageInfo(context);
-	let telemetryReporter: TelemetryReporter = packageInfo && new TelemetryReporter(packageInfo.name, packageInfo.version, packageInfo.aiKey);
+	let telemetryReporter: TelemetryReporter | null = packageInfo && new TelemetryReporter(packageInfo.name, packageInfo.version, packageInfo.aiKey);
 	if (telemetryReporter) {
 		toDispose.push(telemetryReporter);
 	}
@@ -166,7 +166,7 @@ export function activate(context: ExtensionContext) {
 	});
 }
 
-function getPackageInfo(context: ExtensionContext): IPackageInfo {
+function getPackageInfo(context: ExtensionContext): IPackageInfo | null {
 	let extensionPackage = require(context.asAbsolutePath('./package.json'));
 	if (extensionPackage) {
 		return {
diff --git a/extensions/html/client/src/tagClosing.ts b/extensions/html/client/src/tagClosing.ts
index e48a37adf02..174cd460c2c 100644
--- a/extensions/html/client/src/tagClosing.ts
+++ b/extensions/html/client/src/tagClosing.ts
@@ -15,7 +15,7 @@ export function activateTagClosing(tagProvider: (document: TextDocument, positio
 	updateEnabledState();
 	window.onDidChangeActiveTextEditor(updateEnabledState, null, disposables);
 
-	let timeout: NodeJS.Timer = void 0;
+	let timeout: NodeJS.Timer | undefined = void 0;
 
 	function updateEnabledState() {
 		isEnabled = false;
@@ -56,13 +56,15 @@ export function activateTagClosing(tagProvider: (document: TextDocument, positio
 			tagProvider(document, position).then(text => {
 				if (text && isEnabled) {
 					let activeEditor = window.activeTextEditor;
-					let activeDocument = activeEditor && activeEditor.document;
-					if (document === activeDocument && activeDocument.version === version) {
-						let selections = activeEditor.selections;
-						if (selections.length && selections.some(s => s.active.isEqual(position))) {
-							activeEditor.insertSnippet(new SnippetString(text), selections.map(s => s.active));
-						} else {
-							activeEditor.insertSnippet(new SnippetString(text), position);
+					if (activeEditor) {
+						let activeDocument = activeEditor.document;
+						if (document === activeDocument && activeDocument.version === version) {
+							let selections = activeEditor.selections;
+							if (selections.length && selections.some(s => s.active.isEqual(position))) {
+								activeEditor.insertSnippet(new SnippetString(text), selections.map(s => s.active));
+							} else {
+								activeEditor.insertSnippet(new SnippetString(text), position);
+							}
 						}
 					}
 				}
diff --git a/extensions/html/client/src/typings/color-convert.d.ts b/extensions/html/client/src/typings/color-convert.d.ts
deleted file mode 100644
index a88de674d2d..00000000000
--- a/extensions/html/client/src/typings/color-convert.d.ts
+++ /dev/null
@@ -1,11 +0,0 @@
-declare module "color-convert" {
-	module convert {
-		module rgb {
-			function hex(r: number, g: number, b: number);
-			function hsl(r: number, g: number, b: number);
-			function hvs(r: number, g: number, b: number);
-		}
-	}
-
-	export = convert;
-}
\ No newline at end of file
diff --git a/extensions/html/client/tsconfig.json b/extensions/html/client/tsconfig.json
index 31c07df105b..54b6bee6a2a 100644
--- a/extensions/html/client/tsconfig.json
+++ b/extensions/html/client/tsconfig.json
@@ -5,6 +5,7 @@
 		"outDir": "./out",
 		"lib": [
 			"es5", "es2015.promise"
-		]
+		],
+		"strict": true
 	}
 }
\ No newline at end of file
diff --git a/extensions/html/server/src/modes/embeddedSupport.ts b/extensions/html/server/src/modes/embeddedSupport.ts
index 25244863c44..3b524c7c93a 100644
--- a/extensions/html/server/src/modes/embeddedSupport.ts
+++ b/extensions/html/server/src/modes/embeddedSupport.ts
@@ -29,9 +29,9 @@ export function getDocumentRegions(languageService: LanguageService, document: T
 	let regions: EmbeddedRegion[] = [];
 	let scanner = languageService.createScanner(document.getText());
 	let lastTagName: string;
-	let lastAttributeName: string;
-	let languageIdFromType: string;
-	let importedScripts = [];
+	let lastAttributeName: string | null;
+	let languageIdFromType: string | undefined = undefined;
+	let importedScripts: string[] = [];
 
 	let token = scanner.scan();
 	while (token !== TokenType.EOS) {
@@ -224,7 +224,7 @@ function append(result: string, str: string, n: number): string {
 	return result;
 }
 
-function getAttributeLanguage(attributeName: string): string {
+function getAttributeLanguage(attributeName: string): string | null {
 	let match = attributeName.match(/^(style)$|^(on\w+)$/i);
 	if (!match) {
 		return null;
diff --git a/extensions/html/server/src/modes/htmlMode.ts b/extensions/html/server/src/modes/htmlMode.ts
index 38a2abc2367..f3cdab8ee11 100644
--- a/extensions/html/server/src/modes/htmlMode.ts
+++ b/extensions/html/server/src/modes/htmlMode.ts
@@ -60,7 +60,6 @@ export function getHTMLMode(htmlLanguageService: HTMLLanguageService): LanguageM
 			if (offset > 0 && text.charAt(offset - 1).match(/[>\/]/g)) {
 				return htmlLanguageService.doTagComplete(document, position, htmlDocuments.get(document));
 			}
-			return null;
 		},
 		onDocumentRemoved(document: TextDocument) {
 			htmlDocuments.onDocumentRemoved(document);
diff --git a/extensions/html/server/src/modes/javascriptMode.ts b/extensions/html/server/src/modes/javascriptMode.ts
index aad698e91c7..1a53634afbb 100644
--- a/extensions/html/server/src/modes/javascriptMode.ts
+++ b/extensions/html/server/src/modes/javascriptMode.ts
@@ -73,7 +73,7 @@ export function getJavascriptMode(documentRegions: LanguageModelCache<HTMLDocume
 			updateCurrentTextDocument(document);
 			const syntaxDiagnostics = jsLanguageService.getSyntacticDiagnostics(FILE_NAME);
 			const semanticDiagnostics = jsLanguageService.getSemanticDiagnostics(FILE_NAME);
-			return syntaxDiagnostics.concat(semanticDiagnostics).map((diag): Diagnostic => {
+			return syntaxDiagnostics.concat(semanticDiagnostics).map((diag: ts.Diagnostic): Diagnostic => {
 				return {
 					range: convertRange(currentTextDocument, diag),
 					severity: DiagnosticSeverity.Error,
@@ -143,7 +143,7 @@ export function getJavascriptMode(documentRegions: LanguageModelCache<HTMLDocume
 
 					let signature: SignatureInformation = {
 						label: '',
-						documentation: null,
+						documentation: undefined,
 						parameters: []
 					};
 
@@ -185,7 +185,7 @@ export function getJavascriptMode(documentRegions: LanguageModelCache<HTMLDocume
 			let items = jsLanguageService.getNavigationBarItems(FILE_NAME);
 			if (items) {
 				let result: SymbolInformation[] = [];
-				let existing = {};
+				let existing = Object.create(null);
 				let collectSymbols = (item: ts.NavigationBarItem, containerLabel?: string) => {
 					let sig = item.text + item.kind + item.spans[0].start;
 					if (item.kind !== 'script' && !existing[sig]) {
@@ -288,9 +288,13 @@ export function getJavascriptMode(documentRegions: LanguageModelCache<HTMLDocume
 	};
 };
 
-function convertRange(document: TextDocument, span: { start: number, length: number }): Range {
-	let startPosition = document.positionAt(span.start);
-	let endPosition = document.positionAt(span.start + span.length);
+function convertRange(document: TextDocument, span: { start: number | undefined, length: number | undefined }): Range {
+	if (typeof span.start === 'undefined') {
+		const pos = document.positionAt(0);
+		return Range.create(pos, pos);
+	}
+	const startPosition = document.positionAt(span.start);
+	const endPosition = document.positionAt(span.start + (span.length || 0));
 	return Range.create(startPosition, endPosition);
 }
 
diff --git a/extensions/html/server/src/modes/languageModes.ts b/extensions/html/server/src/modes/languageModes.ts
index c151970046f..fdd5585fdc6 100644
--- a/extensions/html/server/src/modes/languageModes.ts
+++ b/extensions/html/server/src/modes/languageModes.ts
@@ -31,7 +31,7 @@ export interface SettingProvider {
 }
 
 export interface LanguageMode {
-	getId();
+	getId(): string;
 	configure?: (options: Settings) => void;
 	doValidation?: (document: TextDocument, settings?: Settings) => Diagnostic[];
 	doComplete?: (document: TextDocument, position: Position, settings?: Settings) => CompletionList;
@@ -74,7 +74,7 @@ export function getLanguageModes(supportedLanguages: { [languageId: string]: boo
 	let modelCaches: LanguageModelCache<any>[] = [];
 	modelCaches.push(documentRegions);
 
-	let modes = {};
+	let modes = Object.create(null);
 	modes['html'] = getHTMLMode(htmlLanguageService);
 	if (supportedLanguages['css']) {
 		modes['css'] = getCSSMode(documentRegions);
diff --git a/extensions/html/server/src/test/javascriptMode.test.ts b/extensions/html/server/src/test/javascriptMode.test.ts
index c5d44e88cae..95a2fb7fbd7 100644
--- a/extensions/html/server/src/test/javascriptMode.test.ts
+++ b/extensions/html/server/src/test/javascriptMode.test.ts
@@ -27,7 +27,7 @@ suite('HTML Javascript Support', () => {
 		var mode = getJavascriptMode(documentRegions);
 
 		let position = document.positionAt(offset);
-		let list = mode.doComplete(document, position);
+		let list = mode.doComplete!(document, position);
 		assert.ok(list);
 
 		let actualLabels = list.items.map(c => c.label).sort();