Update index.md

index.md

@@ -30,7 +30,7 @@ UC Berkeley, Spring 2024
 </div>
 
 <!-- [Zoom links](https://edstem.org/us/courses/25130/discussion/2076738){: .btn .btn-purple }  -->
-[Textbook](econ148.org/textbook){: .btn .btn-blue } [Lecture PollEV](https://pollev.com/ericvandusen){: .btn .btn-purple }
+[Textbook](https://www.econ148.org/textbook){: .btn .btn-blue } [Lecture PollEV](https://pollev.com/ericvandusen){: .btn .btn-purple }
 
 + The schedule and dates listed below are tentative and may be subject to change. 
 + All announcements are on Ed. Make sure you are enrolled and active there.