diff --git a/res/include/style/viewer.css b/res/include/style/viewer.css
index 47d17e9..48fdd7b 100644
--- a/res/include/style/viewer.css
+++ b/res/include/style/viewer.css
@@ -125,6 +125,13 @@
 	transform-origin: 0 0;
 }
 
+/* Pop-up warning (row 5) */
+.file_viewer > .popup_warn {
+	background-color: var(--layer_1_color);
+	border-top: 1px solid var(--layer_1_color_border);
+	text-align: center;
+}
+
 /* Toolbars */
 .file_viewer > .file_viewer_window > .file_viewer_toolbar {
 	position: absolute;
diff --git a/res/template/file_viewer.html b/res/template/file_viewer.html
index d111209..d06465e 100644
--- a/res/template/file_viewer.html
+++ b/res/template/file_viewer.html
@@ -152,6 +152,13 @@
 					</div>
 				{{ end }}
 			</div>
+
+			{{ if and (and .Other.FileAdsEnabled .Other.UserAdsEnabled) (ne .Other.AdPopupType 0) }}
+				<div class="popup_warn">
+					You are viewing a large file ( > 250 MB ). Pop-up ads have been
+					enabled to cover bandwidth cost.
+				</div>
+			{{ end }}
 		</div>
 
 		<template id="tpl_details_popup">
diff --git a/webcontroller/file_viewer.go b/webcontroller/file_viewer.go
index 069a983..08642b3 100644
--- a/webcontroller/file_viewer.go
+++ b/webcontroller/file_viewer.go
@@ -78,12 +78,12 @@ func (vd *viewerData) adType(files []pixelapi.ListFile) {
 	// Intn returns a number up to n, but never n itself. So to get a random 0
 	// or 1 we need to give it n=2. We can use this function to make other
 	// splits like 1/3 1/4, etc
-	switch i := rand.Intn(4); i {
-	case 0: // 25%
+	switch i := rand.Intn(8); i {
+	case 0: // 12.5%
 		vd.AdBannerType = clickAduBanner
-	case 1: // 25%
+	case 1, 2: // 25%
 		vd.AdBannerType = brave
-	case 2, 3: // 50%
+	case 3, 4, 5, 6, 7: // 62.5%
 		vd.AdBannerType = aAds
 	default:
 		panic(fmt.Errorf("random number generator returned unrecognised number: %d", i))