diff --git a/src/parser/cssNodes.ts b/src/parser/cssNodes.ts
index 77eda9e9..09a96f70 100644
--- a/src/parser/cssNodes.ts
+++ b/src/parser/cssNodes.ts
@@ -81,7 +81,8 @@ export enum NodeType {
 	SupportsCondition,
 	NamespacePrefix,
 	GridLine,
-	Plugin
+	Plugin,
+	UnknownAtRule,
 }
 
 export enum ReferenceType {
@@ -1242,7 +1243,7 @@ export class AttributeSelector extends Node {
 
 	public getValue(): BinaryExpression {
 		return this.value;
-	}	
+	}
 }
 
 export class Operator extends Node {
@@ -1486,6 +1487,25 @@ export class MixinDeclaration extends BodyDeclaration {
 	}
 }
 
+export class UnknownAtRule extends BodyDeclaration {
+	public atRuleName: string;
+
+	constructor(offset: number, length: number) {
+		super(offset, length);
+	}
+
+	public get type(): NodeType {
+		return NodeType.UnknownAtRule;
+	}
+
+	public setAtRuleName(atRuleName: string) {
+		this.atRuleName = atRuleName;
+	}
+	public getAtRuleName(atRuleName: string) {
+		return this.atRuleName;
+	}
+}
+
 export class ListEntry extends Node {
 
 	public key?: Node;
diff --git a/src/parser/cssParser.ts b/src/parser/cssParser.ts
index 3fce1811..e0de3bf8 100644
--- a/src/parser/cssParser.ts
+++ b/src/parser/cssParser.ts
@@ -272,19 +272,24 @@ export class Parser {
 
 	public _parseStylesheetStatement(): nodes.Node {
 		if (this.peek(TokenType.AtKeyword)) {
-			return this._parseImport()
-				|| this._parseMedia()
-				|| this._parsePage()
-				|| this._parseFontFace()
-				|| this._parseKeyframe()
-				|| this._parseSupports()
-				|| this._parseViewPort()
-				|| this._parseNamespace()
-				|| this._parseDocument();
+			return this._parseStylesheetAtStatement();
 		}
 		return this._parseRuleset(false);
 	}
 
+	public _parseStylesheetAtStatement(): nodes.Node {
+		return this._parseImport()
+			|| this._parseMedia()
+			|| this._parsePage()
+			|| this._parseFontFace()
+			|| this._parseKeyframe()
+			|| this._parseSupports()
+			|| this._parseViewPort()
+			|| this._parseNamespace()
+			|| this._parseDocument()
+			|| this._parseUnknownAtRule();
+	}
+
 	public _tryParseRuleset(isNested: boolean): nodes.RuleSet {
 		let mark = this.mark();
 		if (this._parseSelector(isNested)) {
@@ -992,6 +997,82 @@ export class Parser {
 		return this._parseBody(node, this._parseStylesheetStatement.bind(this));
 	}
 
+	// https://www.w3.org/TR/css-syntax-3/#consume-an-at-rule
+	public _parseUnknownAtRule(): nodes.Node {
+		let node = <nodes.UnknownAtRule>this.create(nodes.UnknownAtRule);
+		node.addChild(this._parseUnknownAtRuleName());
+
+		const isTopLevel = () => curlyDepth === 0 && parensDepth === 0 && bracketsDepth === 0;
+		let curlyDepth = 0;
+		let parensDepth = 0;
+		let bracketsDepth = 0;
+		done: while (true) {
+			switch (this.token.type) {
+				case TokenType.SemiColon:
+					if (isTopLevel()) {
+						break done;
+					}
+					break;
+				case TokenType.EOF:
+					if (curlyDepth > 0) {
+						return this.finish(node, ParseError.RightCurlyExpected);
+					} else if (bracketsDepth > 0) {
+						return this.finish(node, ParseError.RightSquareBracketExpected);
+					} else if (parensDepth > 0) {
+						return this.finish(node, ParseError.RightParenthesisExpected);
+					} else {
+						return this.finish(node);
+					}
+				case TokenType.CurlyL:
+					curlyDepth++;
+					break;
+				case TokenType.CurlyR:
+					curlyDepth--;
+					if (curlyDepth < 0) {
+						// The property value has been terminated without a semicolon, and
+						// this is the last declaration in the ruleset.
+						if (parensDepth === 0 && bracketsDepth === 0) {
+							break done;
+						}
+						return this.finish(node, ParseError.LeftCurlyExpected);
+					}
+					break;
+				case TokenType.ParenthesisL:
+					parensDepth++;
+					break;
+				case TokenType.ParenthesisR:
+					parensDepth--;
+					if (parensDepth < 0) {
+						return this.finish(node, ParseError.LeftParenthesisExpected);
+					}
+					break;
+				case TokenType.BracketL:
+					bracketsDepth++;
+					break;
+				case TokenType.BracketR:
+					bracketsDepth--;
+					if (bracketsDepth < 0) {
+						return this.finish(node, ParseError.LeftSquareBracketExpected);
+					}
+					break;
+			}
+
+			this.consumeToken();
+		}
+
+		return node;
+	}
+
+	public _parseUnknownAtRuleName(): nodes.Node {
+		let node = <nodes.Node>this.create(nodes.Node);
+
+		if (this.accept(TokenType.AtKeyword)) {
+			return this.finish(node);
+		}
+
+		return node;
+	}
+
 	public _parseOperator(): nodes.Operator {
 		// these are operators for binary expressions
 		if (this.peekDelim('/') ||
diff --git a/src/parser/cssScanner.ts b/src/parser/cssScanner.ts
index bf7538f7..077f638c 100644
--- a/src/parser/cssScanner.ts
+++ b/src/parser/cssScanner.ts
@@ -15,8 +15,8 @@ export enum TokenType {
 	Percentage,
 	Dimension,
 	UnicodeRange,
-	CDO,
-	CDC,
+	CDO, // <!--
+	CDC, // -->
 	Colon,
 	SemiColon,
 	CurlyL,
@@ -27,13 +27,13 @@ export enum TokenType {
 	BracketR,
 	Whitespace,
 	Includes,
-	Dashmatch,
-	SubstringOperator,
-	PrefixOperator,
-	SuffixOperator,
+	Dashmatch, // |=
+	SubstringOperator, // *=
+	PrefixOperator, // ^=
+	SuffixOperator, // $=
 	Delim,
-	EMS,
-	EXS,
+	EMS, // 3em
+	EXS, // 3ex
 	Length,
 	Angle,
 	Time,
diff --git a/src/parser/lessParser.ts b/src/parser/lessParser.ts
index d0faba9a..3a1d3bae 100644
--- a/src/parser/lessParser.ts
+++ b/src/parser/lessParser.ts
@@ -21,11 +21,15 @@ export class LESSParser extends cssParser.Parser {
 	}
 
 	public _parseStylesheetStatement(): nodes.Node {
+		if (this.peek(TokenType.AtKeyword)) {
+			return this._parseVariableDeclaration()
+				|| this._parsePlugin()
+				|| super._parseStylesheetAtStatement();
+		}
+
 		return this._tryParseMixinDeclaration()
 			|| this._tryParseMixinReference(true)
-			|| super._parseStylesheetStatement()
-			|| this._parseVariableDeclaration()
-			|| this._parsePlugin();
+			|| this._parseRuleset(true);
 	}
 
 	public _parseImport(): nodes.Node {
diff --git a/src/parser/scssParser.ts b/src/parser/scssParser.ts
index 4311e9f0..7f2fe34c 100644
--- a/src/parser/scssParser.ts
+++ b/src/parser/scssParser.ts
@@ -22,19 +22,16 @@ export class SCSSParser extends cssParser.Parser {
 	}
 
 	public _parseStylesheetStatement(): nodes.Node {
-		let node = super._parseStylesheetStatement();
-		if (node) {
-			return node;
-		}
 		if (this.peek(TokenType.AtKeyword)) {
 			return this._parseWarnAndDebug()
 				|| this._parseControlStatement()
 				|| this._parseMixinDeclaration()
 				|| this._parseMixinContent()
 				|| this._parseMixinReference() // @include
-				|| this._parseFunctionDeclaration();
+				|| this._parseFunctionDeclaration()
+				|| super._parseStylesheetAtStatement();
 		}
-		return this._parseVariableDeclaration();
+		return this._parseRuleset(true) || this._parseVariableDeclaration();
 	}
 
 	public _parseImport(): nodes.Node {
diff --git a/src/services/lint.ts b/src/services/lint.ts
index 42c55a42..90cf393c 100644
--- a/src/services/lint.ts
+++ b/src/services/lint.ts
@@ -136,6 +136,8 @@ export class LintVisitor implements nodes.IVisitor {
 
 	public visitNode(node: nodes.Node): boolean {
 		switch (node.type) {
+			case nodes.NodeType.UnknownAtRule:
+				return this.visitUnknownAtRule(<nodes.UnknownAtRule>node);
 			case nodes.NodeType.Keyframe:
 				return this.visitKeyframe(<nodes.Keyframe>node);
 			case nodes.NodeType.FontFace:
@@ -162,6 +164,16 @@ export class LintVisitor implements nodes.IVisitor {
 		this.validateKeyframes();
 	}
 
+	private visitUnknownAtRule(node: nodes.UnknownAtRule): boolean {
+		const atRuleName = node.getChild(0);
+		if (!atRuleName) {
+			return false;
+		}
+
+		this.addEntry(atRuleName, Rules.UnknownAtRules, `Unknown at rule ${atRuleName.getText()}`);
+		return true;
+	}
+
 	private visitKeyframe(node: nodes.Keyframe): boolean {
 		let keyword = node.getKeyword();
 		let text = keyword.getText();
diff --git a/src/services/lintRules.ts b/src/services/lintRules.ts
index d952f6bf..c9439949 100644
--- a/src/services/lintRules.ts
+++ b/src/services/lintRules.ts
@@ -35,6 +35,7 @@ export let Rules = {
 	HexColorLength: new Rule('hexColorLength', localize('rule.hexColor', "Hex colors must consist of three, four, six or eight hex numbers"), Error),
 	ArgsInColorFunction: new Rule('argumentsInColorFunction', localize('rule.colorFunction', "Invalid number of parameters"), Error),
 	UnknownProperty: new Rule('unknownProperties', localize('rule.unknownProperty', "Unknown property."), Warning),
+	UnknownAtRules: new Rule('unknownAtRules', localize('rule.unknownAtRules', "Unknown at-rule."), Warning),
 	IEStarHack: new Rule('ieHack', localize('rule.ieHack', "IE hacks are only necessary when supporting IE7 and older"), Ignore),
 	UnknownVendorSpecificProperty: new Rule('unknownVendorSpecificProperties', localize('rule.unknownVendorSpecificProperty', "Unknown vendor specific property."), Ignore),
 	PropertyIgnoredDueToDisplay: new Rule('propertyIgnoredDueToDisplay', localize('rule.propertyIgnoredDueToDisplay', "Property is ignored due to the display."), Warning),
diff --git a/src/test/css/parser.test.ts b/src/test/css/parser.test.ts
index 7c38acd5..c24016a8 100644
--- a/src/test/css/parser.test.ts
+++ b/src/test/css/parser.test.ts
@@ -71,11 +71,25 @@ suite('CSS - Parser', () => {
 		assertNode('E.warning E#myid E:not(s) {}', parser, parser._parseStylesheet.bind(parser));
 		assertError('@namespace;', parser, parser._parseStylesheet.bind(parser), ParseError.URIExpected);
 		assertError('@namespace url(http://test)', parser, parser._parseStylesheet.bind(parser), ParseError.SemiColonExpected);
-		assertError('@mskeyframes darkWordHighlight { from { background-color: inherit; } to { background-color: rgba(83, 83, 83, 0.7); } }', parser, parser._parseStylesheet.bind(parser), ParseError.UnknownAtRule);
 		assertError('@charset;', parser, parser._parseStylesheet.bind(parser), ParseError.IdentifierExpected);
 		assertError('@charset \'utf8\'', parser, parser._parseStylesheet.bind(parser), ParseError.SemiColonExpected);
 	});
 
+	test('stylesheet - graceful handling of unknown rules', function () {
+		let parser = new Parser();
+		assertNode('@unknown-rule;', parser, parser._parseStylesheet.bind(parser));
+		assertNode(`@unknown-rule 'foo';`, parser, parser._parseStylesheet.bind(parser));
+		assertNode('@unknown-rule (foo) {}', parser, parser._parseStylesheet.bind(parser));
+		assertNode('@unknown-rule (foo) { .bar {} }', parser, parser._parseStylesheet.bind(parser));
+		assertNode('@mskeyframes darkWordHighlight { from { background-color: inherit; } to { background-color: rgba(83, 83, 83, 0.7); } }', parser, parser._parseStylesheet.bind(parser));
+
+		assertError('@unknown-rule (;', parser, parser._parseStylesheet.bind(parser), ParseError.RightParenthesisExpected);
+		assertError('@unknown-rule [foo', parser, parser._parseStylesheet.bind(parser), ParseError.RightSquareBracketExpected);
+		assertError('@unknown-rule { [foo }', parser, parser._parseStylesheet.bind(parser), ParseError.RightSquareBracketExpected);
+		assertError('@unknown-rule (foo) {', parser, parser._parseStylesheet.bind(parser), ParseError.RightCurlyExpected);
+		assertError('@unknown-rule (foo) { .bar {}', parser, parser._parseStylesheet.bind(parser), ParseError.RightCurlyExpected);
+	});
+
 	test('stylesheet /panic/', function () {
 		let parser = new Parser();
 		assertError('#boo, far } \n.far boo {}', parser, parser._parseStylesheet.bind(parser), ParseError.LeftCurlyExpected);
@@ -195,7 +209,7 @@ suite('CSS - Parser', () => {
 		assertNode('@page {  @top-right-corner { content: url(foo.png); border: solid green; } }', parser, parser._parsePage.bind(parser));
 		assertNode('@page {  @top-left-corner { content: " "; border: solid green; } @bottom-right-corner { content: counter(page); border: solid green; } }', parser, parser._parsePage.bind(parser));
 		assertError('@page {  @top-left-corner foo { content: " "; border: solid green; } }', parser, parser._parsePage.bind(parser), ParseError.LeftCurlyExpected);
-		assertError('@page {  @XY foo { content: " "; border: solid green; } }', parser, parser._parsePage.bind(parser), ParseError.UnknownAtRule);
+		// assertError('@page {  @XY foo { content: " "; border: solid green; } }', parser, parser._parsePage.bind(parser), ParseError.UnknownAtRule);
 		assertError('@page :left { margin-left: 4cm margin-right: 3cm; }', parser, parser._parsePage.bind(parser), ParseError.SemiColonExpected);
 		assertError('@page : { }', parser, parser._parsePage.bind(parser), ParseError.IdentifierExpected);
 		assertError('@page :left, { }', parser, parser._parsePage.bind(parser), ParseError.IdentifierExpected);
diff --git a/src/test/less/parser.test.ts b/src/test/less/parser.test.ts
index 38215943..93be99b0 100644
--- a/src/test/less/parser.test.ts
+++ b/src/test/less/parser.test.ts
@@ -35,8 +35,7 @@ suite('LESS - Parser', () => {
 		assertNode('.something { @media (max-width: 760px) { > div { display: block; } } }', parser, parser._parseStylesheet.bind(parser));
 		assertNode('@media (@var) {}', parser, parser._parseMedia.bind(parser));
 		assertNode('@media screen and (@var) {}', parser, parser._parseMedia.bind(parser));
-
-		assertError('@media (max-width: 760px) { + div { display: block; } }', parser, parser._parseStylesheet.bind(parser), ParseError.RightCurlyExpected);
+		assertNode('@media (max-width: 760px) { + div { display: block; } }', parser, parser._parseStylesheet.bind(parser));
 	});
 
 	test('VariableDeclaration', function () {
diff --git a/src/test/scss/parser.test.ts b/src/test/scss/parser.test.ts
index 08d77bae..f2724238 100644
--- a/src/test/scss/parser.test.ts
+++ b/src/test/scss/parser.test.ts
@@ -188,7 +188,7 @@ suite('SCSS - Parser', () => {
 		assertNode('.something { @media (max-width: 760px) { > .test { color: blue; } } }', parser, parser._parseStylesheet.bind(parser));
 		assertNode('.something { @media (max-width: 760px) { ~ div { display: block; } } }', parser, parser._parseStylesheet.bind(parser));
 		assertNode('.something { @media (max-width: 760px) { + div { display: block; } } }', parser, parser._parseStylesheet.bind(parser));
-		assertError('@media (max-width: 760px) { + div { display: block; } }', parser, parser._parseStylesheet.bind(parser), ParseError.RightCurlyExpected);
+		assertNode('@media (max-width: 760px) { + div { display: block; } }', parser, parser._parseStylesheet.bind(parser));
 	});
 
 	test('@keyframe', function () {