diff --git a/src/interfaces.ts b/src/interfaces.ts
index 07bca42ca0..acb9671499 100644
--- a/src/interfaces.ts
+++ b/src/interfaces.ts
@@ -54,7 +54,7 @@ export interface CompileOptions {
 	cascade?: boolean;
 	hydratable?: boolean;
 	legacy?: boolean;
-	customElement: CustomElementOptions | true;
+	customElement?: CustomElementOptions | true;
 
 	onerror?: (error: Error) => void;
 	onwarn?: (warning: Warning) => void;
diff --git a/src/validate/html/index.ts b/src/validate/html/index.ts
index ad653daa63..186181e913 100644
--- a/src/validate/html/index.ts
+++ b/src/validate/html/index.ts
@@ -1,4 +1,3 @@
-import * as namespaces from '../../utils/namespaces';
 import validateElement from './validateElement';
 import validateWindow from './validateWindow';
 import fuzzymatch from '../utils/fuzzymatch'
@@ -6,36 +5,20 @@ import flattenReference from '../../utils/flattenReference';
 import { Validator } from '../index';
 import { Node } from '../../interfaces';
 
-const svg = /^(?:altGlyph|altGlyphDef|altGlyphItem|animate|animateColor|animateMotion|animateTransform|circle|clipPath|color-profile|cursor|defs|desc|discard|ellipse|feBlend|feColorMatrix|feComponentTransfer|feComposite|feConvolveMatrix|feDiffuseLighting|feDisplacementMap|feDistantLight|feDropShadow|feFlood|feFuncA|feFuncB|feFuncG|feFuncR|feGaussianBlur|feImage|feMerge|feMergeNode|feMorphology|feOffset|fePointLight|feSpecularLighting|feSpotLight|feTile|feTurbulence|filter|font|font-face|font-face-format|font-face-name|font-face-src|font-face-uri|foreignObject|g|glyph|glyphRef|hatch|hatchpath|hkern|image|line|linearGradient|marker|mask|mesh|meshgradient|meshpatch|meshrow|metadata|missing-glyph|mpath|path|pattern|polygon|polyline|radialGradient|rect|set|solidcolor|stop|switch|symbol|text|textPath|title|tref|tspan|unknown|use|view|vkern)$/;
-
 const meta = new Map([[':Window', validateWindow]]);
 
 export default function validateHtml(validator: Validator, html: Node) {
-	let elementDepth = 0;
-
 	const refs = new Map();
 	const refCallees: Node[] = [];
+	const elementStack: Node[] = [];
 
 	function visit(node: Node) {
 		if (node.type === 'Element') {
-			if (
-				elementDepth === 0 &&
-				validator.namespace !== namespaces.svg &&
-				svg.test(node.name)
-			) {
-				validator.warn(
-					`<${node.name}> is an SVG element – did you forget to add { namespace: 'svg' } ?`,
-					node.start
-				);
-			}
-
 			if (meta.has(node.name)) {
 				return meta.get(node.name)(validator, node, refs, refCallees);
 			}
 
-			elementDepth += 1;
-
-			validateElement(validator, node, refs, refCallees);
+			validateElement(validator, node, refs, refCallees, elementStack);
 		} else if (node.type === 'EachBlock') {
 			if (validator.helpers.has(node.context)) {
 				let c = node.expression.end;
@@ -53,16 +36,14 @@ export default function validateHtml(validator: Validator, html: Node) {
 		}
 
 		if (node.children) {
+			if (node.type === 'Element') elementStack.push(node);
 			node.children.forEach(visit);
+			if (node.type === 'Element') elementStack.pop();
 		}
 
 		if (node.else) {
 			visit(node.else);
 		}
-
-		if (node.type === 'Element') {
-			elementDepth -= 1;
-		}
 	}
 
 	html.children.forEach(visit);
diff --git a/src/validate/html/validateElement.ts b/src/validate/html/validateElement.ts
index 3641280f19..aa396bac0a 100644
--- a/src/validate/html/validateElement.ts
+++ b/src/validate/html/validateElement.ts
@@ -1,8 +1,17 @@
+import * as namespaces from '../../utils/namespaces';
 import validateEventHandler from './validateEventHandler';
 import { Validator } from '../index';
 import { Node } from '../../interfaces';
 
-export default function validateElement(validator: Validator, node: Node, refs: Map<string, Node[]>, refCallees: Node[]) {
+const svg = /^(?:altGlyph|altGlyphDef|altGlyphItem|animate|animateColor|animateMotion|animateTransform|circle|clipPath|color-profile|cursor|defs|desc|discard|ellipse|feBlend|feColorMatrix|feComponentTransfer|feComposite|feConvolveMatrix|feDiffuseLighting|feDisplacementMap|feDistantLight|feDropShadow|feFlood|feFuncA|feFuncB|feFuncG|feFuncR|feGaussianBlur|feImage|feMerge|feMergeNode|feMorphology|feOffset|fePointLight|feSpecularLighting|feSpotLight|feTile|feTurbulence|filter|font|font-face|font-face-format|font-face-name|font-face-src|font-face-uri|foreignObject|g|glyph|glyphRef|hatch|hatchpath|hkern|image|line|linearGradient|marker|mask|mesh|meshgradient|meshpatch|meshrow|metadata|missing-glyph|mpath|path|pattern|polygon|polyline|radialGradient|rect|set|solidcolor|stop|switch|symbol|text|textPath|title|tref|tspan|unknown|use|view|vkern)$/;
+
+export default function validateElement(
+	validator: Validator,
+	node: Node,
+	refs: Map<string, Node[]>,
+	refCallees: Node[],
+	elementStack: Node[]
+) {
 	const isComponent =
 		node.name === ':Self' || validator.components.has(node.name);
 
@@ -11,6 +20,13 @@ export default function validateElement(validator: Validator, node: Node, refs:
 		validator.warn(`${node.name} component is not defined`, node.start);
 	}
 
+	if (elementStack.length === 0 && validator.namespace !== namespaces.svg && svg.test(node.name)) {
+		validator.warn(
+			`<${node.name}> is an SVG element – did you forget to add { namespace: 'svg' } ?`,
+			node.start
+		);
+	}
+
 	if (node.name === 'slot') {
 		const nameAttribute = node.attributes.find((attribute: Node) => attribute.name === 'name');
 		if (nameAttribute) {
@@ -44,6 +60,8 @@ export default function validateElement(validator: Validator, node: Node, refs:
 	let hasOutro: boolean;
 	let hasTransition: boolean;
 
+	const attributeMap: Map<string, Node> = new Map();
+
 	node.attributes.forEach((attribute: Node) => {
 		if (attribute.type === 'Ref') {
 			if (!refs.has(attribute.name)) refs.set(attribute.name, []);
@@ -161,6 +179,8 @@ export default function validateElement(validator: Validator, node: Node, refs:
 				);
 			}
 		} else if (attribute.type === 'Attribute') {
+			attributeMap.set(attribute.name, attribute);
+
 			if (attribute.name === 'value' && node.name === 'textarea') {
 				if (node.children.length) {
 					validator.error(
@@ -178,6 +198,29 @@ export default function validateElement(validator: Validator, node: Node, refs:
 			}
 		}
 	});
+
+	// a11y
+	if (node.name === 'a' && !attributeMap.has('href')) {
+		validator.warn(`A11y: <a> element should have an href attribute`, node.start);
+	}
+
+	if (node.name === 'img' && !attributeMap.has('alt')) {
+		validator.warn(`A11y: <img> element should have an alt attribute`, node.start);
+	}
+
+	if (node.name === 'figcaption') {
+		const parent = elementStack[elementStack.length - 1];
+		if (parent) {
+			if (parent.name !== 'figure') {
+				validator.warn(`A11y: <figcaption> must be an immediate child of <figure>`, node.start);
+			} else {
+				const index = parent.children.indexOf(node);
+				if (index !== 0 && index !== parent.children.length - 1) {
+					validator.warn(`A11y: <figcaption> must be first or last child of <figure>`, node.start);
+				}
+			}
+		}
+	}
 }
 
 function checkTypeAttribute(validator: Validator, node: Node) {
diff --git a/test/validator/index.js b/test/validator/index.js
index 176d060faf..1c718fae80 100644
--- a/test/validator/index.js
+++ b/test/validator/index.js
@@ -2,7 +2,7 @@ import * as fs from "fs";
 import assert from "assert";
 import { svelte, tryToLoadJson } from "../helpers.js";
 
-describe("validate", () => {
+describe.only("validate", () => {
 	fs.readdirSync("test/validator/samples").forEach(dir => {
 		if (dir[0] === ".") return;
 
diff --git a/test/validator/samples/a11y-a-without-href/input.html b/test/validator/samples/a11y-a-without-href/input.html
new file mode 100644
index 0000000000..f7ebe13def
--- /dev/null
+++ b/test/validator/samples/a11y-a-without-href/input.html
@@ -0,0 +1 @@
+<a>not actually a link</a>
\ No newline at end of file
diff --git a/test/validator/samples/a11y-a-without-href/warnings.json b/test/validator/samples/a11y-a-without-href/warnings.json
new file mode 100644
index 0000000000..bf5f650ba5
--- /dev/null
+++ b/test/validator/samples/a11y-a-without-href/warnings.json
@@ -0,0 +1,8 @@
+[{
+	"message": "A11y: <a> element should have an href attribute",
+	"loc": {
+		"line": 1,
+		"column": 0
+	},
+	"pos": 0
+}]
\ No newline at end of file
diff --git a/test/validator/samples/a11y-figcaption-wrong-place/input.html b/test/validator/samples/a11y-figcaption-wrong-place/input.html
new file mode 100644
index 0000000000..ffa7dde65d
--- /dev/null
+++ b/test/validator/samples/a11y-figcaption-wrong-place/input.html
@@ -0,0 +1,19 @@
+<figure>
+	<img src='foo.jpg' alt='a picture of a foo'>
+
+	<figcaption>
+		a foo in its natural habitat
+	</figcaption>
+
+	<p>this should not be here</p>
+</figure>
+
+<figure>
+	<img src='foo.jpg' alt='a picture of a foo'>
+
+	<div class='markup-for-styling'>
+		<figcaption>
+			this element should be a child of the figure
+		</figcaption>
+	</div>
+</figure>
\ No newline at end of file
diff --git a/test/validator/samples/a11y-figcaption-wrong-place/warnings.json b/test/validator/samples/a11y-figcaption-wrong-place/warnings.json
new file mode 100644
index 0000000000..0e5e1a1976
--- /dev/null
+++ b/test/validator/samples/a11y-figcaption-wrong-place/warnings.json
@@ -0,0 +1,18 @@
+[
+	{
+		"message": "A11y: <figcaption> must be first or last child of <figure>",
+		"loc": {
+			"line": 4,
+			"column": 1
+		},
+		"pos": 57
+	},
+	{
+		"message": "A11y: <figcaption> must be an immediate child of <figure>",
+		"loc": {
+			"line": 15,
+			"column": 2
+		},
+		"pos": 252
+	}
+]
diff --git a/test/validator/samples/a11y-img-without-alt/input.html b/test/validator/samples/a11y-img-without-alt/input.html
new file mode 100644
index 0000000000..4e524fe107
--- /dev/null
+++ b/test/validator/samples/a11y-img-without-alt/input.html
@@ -0,0 +1 @@
+<img src='foo.jpg'>
\ No newline at end of file
diff --git a/test/validator/samples/a11y-img-without-alt/warnings.json b/test/validator/samples/a11y-img-without-alt/warnings.json
new file mode 100644
index 0000000000..9c48172925
--- /dev/null
+++ b/test/validator/samples/a11y-img-without-alt/warnings.json
@@ -0,0 +1,8 @@
+[{
+	"message": "A11y: <img> element should have an alt attribute",
+	"loc": {
+		"line": 1,
+		"column": 0
+	},
+	"pos": 0
+}]
\ No newline at end of file