Use class instead of ID.

app.py

@@ -196,7 +196,7 @@ with blocks:
         show_label=False,
         show_download_button=False,
         container=False,
-        elem_id="banner_image",
+        elem_classes=["banner_image"],
     )
 
     gr.HTML(

src/display/css_html_js.py

@@ -4,7 +4,7 @@ custom_css = """
     font-size: 16px !important;
 }
 
-#banner_image { width: 70% !important; }
+.banner_image { width: 70% !important; }
 
 @import url('https://fonts.googleapis.com/css2?family=Exo+2:wght@500;600&display=swap');