diff --git a/404.html b/404.html
index 9b7596f..bd1bc63 100644
--- a/404.html
+++ b/404.html
@@ -3,11 +3,12 @@
 
 <head>
     <meta charset="UTF-8">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Page Not Found - Image & Video Tools</title>
     <link rel="stylesheet" href="https://hoangsonww.github.io/Image-Video-Tools/src/css/common.css">
     <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.15.3/css/all.min.css">
     <meta name="description" content="The page you requested was not found on Image & Video Tools.">
+    <link rel="manifest" href="https://hoangsonww.github.io/Image-Video-Tools/manifest.json">
     <meta name="theme-color" content="#007bff">
     <link rel="icon" type="image/x-icon" href="https://hoangsonww.github.io/Image-Video-Tools/assets/favicon.ico">
     <style>
@@ -21,6 +22,16 @@
     </style>
 </head>
 
+<!-- Google tag (gtag.js) -->
+<script async src="https://www.googletagmanager.com/gtag/js?id=G-N2PN8MEEQV"></script>
+<script>
+    window.dataLayer = window.dataLayer || [];
+    function gtag(){dataLayer.push(arguments);}
+    gtag('js', new Date());
+
+    gtag('config', 'G-N2PN8MEEQV');
+</script>
+
 <body>
     <div id="navbar">
         <a id="header-link" href="https://hoangsonww.github.io/Image-Video-Tools/index.html">
diff --git a/index.html b/index.html
index c12fa70..f9f175d 100644
--- a/index.html
+++ b/index.html
@@ -3,7 +3,7 @@
 
 <head>
     <meta charset="UTF-8">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Image & Video Tools: Unleash the Power of Media</title>
     <script src="src/js/resizer.js"></script>
 
diff --git a/src/html/about.html b/src/html/about.html
index 728021a..2afa203 100644
--- a/src/html/about.html
+++ b/src/html/about.html
@@ -3,7 +3,7 @@
 
 <head>
     <meta charset="UTF-8">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>About - Image & Video Tools: Unleash the Power of Media</title>
     <link rel="stylesheet" href="../css/common.css">
     <link rel="stylesheet" href="../css/about.css">
diff --git a/src/html/background-remover.html b/src/html/background-remover.html
index 6527199..94f59bd 100644
--- a/src/html/background-remover.html
+++ b/src/html/background-remover.html
@@ -3,7 +3,7 @@
 
 <head>
     <meta charset="UTF-8">
-    <meta name="viewport" content="width=device=width, initial-scale=1.0">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Image & Video Tools: Unleash the Power of Media</title>
     <link rel="stylesheet" href="../css/common.css">
     <link rel="stylesheet" href="../css/bg-remover.css">
diff --git a/src/html/converter.html b/src/html/converter.html
index b62c792..65307f9 100644
--- a/src/html/converter.html
+++ b/src/html/converter.html
@@ -3,7 +3,7 @@
 
 <head>
     <meta charset="UTF-8">
-    <meta name="viewport" content="width=device=width, initial-scale=1.0">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Image & Video Tools: Unleash the Power of Media</title>
     <link rel="stylesheet" href="../css/common.css">
     <link rel="stylesheet" href="../css/converter.css">
diff --git a/src/html/cropper.html b/src/html/cropper.html
index 9c1d560..c5ec005 100644
--- a/src/html/cropper.html
+++ b/src/html/cropper.html
@@ -3,7 +3,7 @@
 
 <head>
     <meta charset="UTF-8">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Image & Video Tools: Unleash the Power of Media</title>
     <link rel="icon" type="image/x-icon" href="../../assets/favicon.ico">
     <link rel="stylesheet" href="../css/common.css">
diff --git a/src/html/filter.html b/src/html/filter.html
index e89a5f5..23befa5 100644
--- a/src/html/filter.html
+++ b/src/html/filter.html
@@ -3,7 +3,7 @@
 
 <head>
     <meta charset="UTF-8">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Image & Video Tools: Unleash the Power of Media</title>
     <script src="../js/resizer.js"></script>
     <link rel="stylesheet" href="../css/common.css">
diff --git a/src/html/rotator.html b/src/html/rotator.html
index 07b20d7..b9a5251 100644
--- a/src/html/rotator.html
+++ b/src/html/rotator.html
@@ -3,7 +3,7 @@
 
 <head>
     <meta charset="UTF-8">
-    <meta name="viewport" content="width=device=width, initial-scale=1.0">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Image & Video Tools: Unleash the Power of Media</title>
     <link rel="stylesheet" href="../css/common.css">
     <link rel="icon" type="image/x-icon" href="../../assets/favicon.ico">
diff --git a/src/html/sound-remover.html b/src/html/sound-remover.html
index 5b04651..8df4634 100644
--- a/src/html/sound-remover.html
+++ b/src/html/sound-remover.html
@@ -3,7 +3,7 @@
 
     <head>
         <meta charset="UTF-8">
-        <meta name="viewport" content="width=device=width, initial-scale=1.0">
+        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
         <title>Image & Video Tools: Unleash the Power of Media</title>
         <link rel="stylesheet" href="../css/common.css">
         <link rel="icon" type="image/x-icon" href="../../assets/favicon.ico">
diff --git a/src/html/thumbnail-generator.html b/src/html/thumbnail-generator.html
index 7f74370..a61be27 100644
--- a/src/html/thumbnail-generator.html
+++ b/src/html/thumbnail-generator.html
@@ -3,7 +3,7 @@
 
 <head>
     <meta charset="UTF-8">
-    <meta name="viewport" content="width=device=width, initial-scale=1.0">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Image & Video Tools: Unleash the Power of Media</title>
     <link rel="stylesheet" href="../css/common.css">
     <link rel="icon" type="image/x-icon" href="../../assets/favicon.ico">
diff --git a/src/html/watermarker.html b/src/html/watermarker.html
index f238220..59694ad 100644
--- a/src/html/watermarker.html
+++ b/src/html/watermarker.html
@@ -3,7 +3,7 @@
 
 <head>
     <meta charset="UTF-8">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Image & Video Tools: Unleash the Power of Media</title>
     <link rel="stylesheet" href="../css/common.css">
     <link rel="icon" type="image/x-icon" href="../../assets/favicon.ico">
diff --git a/src/js/background-remover.js b/src/js/background-remover.js
index 7c5368b..ce3c1c4 100644
--- a/src/js/background-remover.js
+++ b/src/js/background-remover.js
@@ -69,7 +69,7 @@ document.addEventListener('DOMContentLoaded', () => {
             })
             .catch(error => {
                 console.error('Error:', error);
-                message.textContent = 'Error removing background. Please try again.';
+                message.textContent = 'Error removing background. Your image might not have a clear subject. Please try again with a different image.';
                 message.style.display = 'block';
             })
             .finally(() => {
