-<input name="embed_size_h" type="text" id="embed_size_h" value="<?php form_option('embed_size_h'); ?>" class="small-text" />
-<?php if ( !empty($content_width) ) echo '<br />' . __("If the width value is left blank, embeds will default to the max width of your theme."); ?>
+<input name="embed_size_h" type="number" step="1" min="0" id="embed_size_h" value="<?php form_option('embed_size_h'); ?>" class="small-text" />
+<?php if ( ! empty( $content_width ) )
+ echo '<p class="description">' . __( 'If the width value is left blank, embeds will default to the max width of your theme.' ) . '</p>';
+?>