diff --git a/index.html b/index.html
index 2539e3e..7ab17b1 100644
--- a/index.html
+++ b/index.html
@@ -457,7 +457,11 @@
                         </button>
                     </div>
                     <div class="modal-body">
-                        <p id="nogoError" style="display: none;"></p>
+                        <p
+                            id="nogoError"
+                            class="invalid-feedback"
+                            style="display: none;"
+                        ></p>
                         <form>
                             <fieldset>
                                 <legend data-i18n="loadNogos.source">
diff --git a/js/index.js b/js/index.js
index 805968d..6974ad5 100644
--- a/js/index.js
+++ b/js/index.js
@@ -425,30 +425,37 @@
                     reader.onload = function() {
                         resolve(reader.result);
                     };
+                    reader.onerror = function() {
+                        $('#nogoError').text(
+                            'Cannot read file: ' + reader.error.message
+                        );
+                        $('#nogoError').css('display', 'block');
+                    };
+
                     reader.readAsText(nogoFile);
                 }).then(function(response) {
                     return JSON.parse(response);
                 });
             } else {
-                $('#nogoError').text('Error: Missing file or URL.');
+                $('#nogoError').text('Missing file or URL.');
                 $('#nogoError').css('display', 'block');
                 return false;
             }
             var nogoWeight = parseFloat($('#nogoWeight').val());
             if (isNaN(nogoWeight)) {
-                $('#nogoError').text('Error: Missing default nogo weight.');
+                $('#nogoError').text('Missing default nogo weight.');
                 $('#nogoError').css('display', 'block');
                 return false;
             }
             var nogoRadius = parseFloat($('#nogoRadius').val());
             if (isNaN(nogoRadius) || nogoRadius < 0) {
-                $('#nogoError').text('Error: Invalid default nogo radius.');
+                $('#nogoError').text('Invalid default nogo radius.');
                 $('#nogoError').css('display', 'block');
                 return false;
             }
             var nogoBuffer = parseFloat($('#nogoBuffer').val());
             if (isNaN(nogoBuffer)) {
-                $('#nogoError').text('Error: Invalid nogo buffering radius.');
+                $('#nogoError').text('Invalid nogo buffering radius.');
                 $('#nogoError').css('display', 'block');
                 return false;
             }
@@ -471,6 +478,14 @@
                     }
                 });
 
+                if (cleanedGeoJSONFeatures.length === 0) {
+                    $('#nogoError').text(
+                        'No valid area found in provided input.'
+                    );
+                    $('#nogoError').css('display', 'block');
+                    return false;
+                }
+
                 var geoJSON = L.geoJson(
                     turf.featureCollection(cleanedGeoJSONFeatures),
                     {