diff --git a/apps/school/templates/school/livelesson_detail.html b/apps/school/templates/school/livelesson_detail.html
index 25211945..e5229ada 100644
--- a/apps/school/templates/school/livelesson_detail.html
+++ b/apps/school/templates/school/livelesson_detail.html
@@ -10,10 +10,10 @@
       <div class="lesson__content">{{ livelesson.short_description }}</div>
       <a class="lesson__video video" href="#">
         {% if livelesson.is_online %}
-        <iframe src="https://player.vimeo.com/video/{{ livelesson.stream_index }}" width="640" height="360" frameborder="0" webkitallowfullscreen
+        <iframe class="lesson__video_frame" src="https://player.vimeo.com/video/{{ livelesson.stream_index }}" frameborder="0" webkitallowfullscreen
           mozallowfullscreen allowfullscreen>
         </iframe>
-        <iframe src="https://vimeo.com/live-chat/{{ livelesson.stream_index }}" width="600" height="600" frameborder="0"></iframe>
+        <iframe class="lesson__chat_frame" src="https://vimeo.com/live-chat/{{ livelesson.stream_index }}" frameborder="0"></iframe>
         {% else %}
         {% if livelesson.cover %}
         <img class="video__pic" src="{{ livelesson.cover.image.url }}"/>
diff --git a/web/src/sass/_common.sass b/web/src/sass/_common.sass
index fae1cb73..cc6f3fa7 100755
--- a/web/src/sass/_common.sass
+++ b/web/src/sass/_common.sass
@@ -2658,6 +2658,17 @@ a.grey-link
   &__content
     margin-bottom: 30px
     color: #191919
+  &__video_frame
+    width: 640px
+    height: 360px
+    +m
+      width: 100%
+  &__chat_frame
+    width: 600px
+    height: 600px
+    +m
+      width: 100%
+
 
 .lessons
   &__subtitle