diff --git a/classes/Feeds.php b/classes/Feeds.php
index 6284b1b8f..8f1fa5d9f 100644
--- a/classes/Feeds.php
+++ b/classes/Feeds.php
@@ -1013,7 +1013,10 @@ class Feeds extends Handler_Protected {
 
 		$url = UrlHelper::validate($url);
 
-		if (!$url) return ["code" => 2];
+		if (!$url) {
+			Logger::log(E_USER_NOTICE, "An attempt to subscribe to '{$url}' failed due to URL validation (User: '{$user->login}'; ID: {$user->id}).");
+			return ["code" => 2];
+		}
 
 		PluginHost::getInstance()->chain_hooks_callback(PluginHost::HOOK_PRE_SUBSCRIBE,
 			/** @phpstan-ignore closure.unusedUse, closure.unusedUse, closure.unusedUse */
@@ -1035,14 +1038,20 @@ class Feeds extends Handler_Protected {
 				UrlHelper::$fetch_last_error .= " (feed behind Cloudflare)";
 			}
 
-			return array("code" => 5, "message" => truncate_string(UrlHelper::$fetch_last_error, 1000, '…'));
+			Logger::log(E_USER_NOTICE, "An attempt to subscribe to '{$url}' failed (User: '{$user->login}'; ID: {$user->id}).",
+				truncate_string(UrlHelper::$fetch_last_error, 500, '…'));
+
+			return array("code" => 5, "message" => truncate_string(clean(UrlHelper::$fetch_last_error), 250, '…'));
 		}
 
 		if (str_contains(UrlHelper::$fetch_last_content_type, "html") && self::_is_html($contents)) {
 			$feedUrls = self::_get_feeds_from_html($url, $contents);
 
 			if (count($feedUrls) == 0) {
-				return array("code" => 3, "message" => truncate_string($contents, 1000, '…'));
+				Logger::log(E_USER_NOTICE, "An attempt to subscribe to '{$url}' failed due to content being HTML without detected feed URLs (User: '{$user->login}'; ID: {$user->id}).",
+					truncate_string($contents, 500, '…'));
+
+				return array("code" => 3, "message" => truncate_string(clean($contents), 250, '…'));
 			} else if (count($feedUrls) > 1) {
 				return array("code" => 4, "feeds" => $feedUrls);
 			}
diff --git a/js/CommonDialogs.js b/js/CommonDialogs.js
index eaa0249e8..1215d567d 100644
--- a/js/CommonDialogs.js
+++ b/js/CommonDialogs.js
@@ -118,10 +118,10 @@ const	CommonDialogs = {
 									</footer>
 								</form>
 							`,
-							show_error: function (msg) {
+							show_error: function (msg, additional_info) {
 								const elem = App.byId("fadd_error_message");
 
-								elem.innerHTML = msg;
+								elem.innerHTML = `${msg}${additional_info ? `<br><br><h4>${__('Additional information')}</h4>${additional_info}` : ''}`;
 
 								Element.show(elem);
 							},
@@ -168,9 +168,7 @@ const	CommonDialogs = {
 													dialog.show_error(__("Specified URL seems to be invalid."));
 													break;
 												case 3:
-													dialog.show_error(`<span title="${App.escapeHtml(rc['message'])}" style="text-decoration: underline dotted">
-														${__("Specified URL doesn't seem to contain any feeds.")}
-														</span>`);
+													dialog.show_error(__("Specified URL doesn't seem to contain any feeds."), App.escapeHtml(rc['message']));
 													break;
 												case 4:
 													{
@@ -195,7 +193,7 @@ const	CommonDialogs = {
 													}
 													break;
 												case 5:
-													dialog.show_error(__("Couldn't download the specified URL: %s").replace("%s", App.escapeHtml(rc['message'])));
+													dialog.show_error(__("Couldn't download the specified URL."), App.escapeHtml(rc['message']));
 													break;
 												case 7:
 													dialog.show_error(__("Error while creating feed database entry."));