update bookdowm doc
diff --git a/docs/bookdown_example/_output.yml b/docs/bookdown_example/_output.yml
index 0027923..856d2f1 100644
--- a/docs/bookdown_example/_output.yml
+++ b/docs/bookdown_example/_output.yml
@@ -1,4 +1,5 @@
 bookdown::gitbook:
+  table_css: false
   config:
     download: ["pdf", "epub"]
 bookdown::pdf_book: