diff --git a/server/src/Patterns.ts b/server/src/Patterns.ts
index 2a515c4..02460be 100644
--- a/server/src/Patterns.ts
+++ b/server/src/Patterns.ts
@@ -17,7 +17,8 @@ const patterns: string[] = [
 	"<img(?:.)+?>",
 	"<input(?:.)+?>",
 	"<head(?:.|)+?>(?:(?:\\s|\\S|)+?(?=<\/head>))<\/head>",
-	"<html(?:.)+?>"
+	"<html(?:.)+?>",
+	"tabindex=\"(?:.)+?\""
 ];
 export const pattern: RegExp = new RegExp(patterns.join('|'), 'ig');
 
@@ -205,7 +206,7 @@ export async function validateInput(m: RegExpExecArray) {
 			} else {
 				return {
 					meta: m,
-					mess: 'Provide an id with in the aria labelled by [aria-labelledby=""]'
+					mess: 'Provide an id with in the aria labelledby [aria-labelledby=""]'
 				};
 			}
 		case (/role=/i.test(m[0])):
@@ -217,4 +218,14 @@ export async function validateInput(m: RegExpExecArray) {
 				mess: 'Provide an aria label [aria-label=""]'
 			};
 	}
+}
+
+export async function validateTab(m: RegExpExecArray) {
+	connection.console.log(m[0]);
+	if (!/tabindex="(?:0|-1)"/i.test(m[0])) {
+		return {
+			meta: m,
+			mess: 'A tabindex greater than 0 interferes with the focus order. Try restructuring the HTML'
+		};
+	}
 }
\ No newline at end of file
diff --git a/server/src/server.ts b/server/src/server.ts
index 74d840a..65dfb89 100644
--- a/server/src/server.ts
+++ b/server/src/server.ts
@@ -168,6 +168,14 @@ async function validateTextDocument(textDocument: TextDocument): Promise<void> {
 						_diagnostics(resultHtml.meta, resultHtml.mess);
 					}
 					break;
+				// Tabindex
+				case (/tabin/i.test(el)):
+					let resultTab = await Pattern.validateTab(m);
+					if (resultTab) {
+						problems++;
+						_diagnostics(resultTab.meta, resultTab.mess);
+					}
+					break;
 				default:
 					break;
 			}