1. From Web, click Page Designer 
  2. Click Next
  3. Click Advance colors and styles
  4. Click Edit style sheet
  5. Scroll to the bottom of the editor
  6. Insert the following code:

                           .MembershipExpress_TypeContainer {display:none;}
  7. Click Apply
  8. Click Save
  9. Click Next
  10. Click Submit

If you would like to remove Membership Type entirely from web forms, rather than hiding it, we have an idea on our Community regarding this: https://altru.ideas.aha.io/ideas/ALTRU-I-639 We encourage you to vote on this post as this is an opportunity to have a voice in the product development process.  Our Product Management team uses a variety of methods to determine new features in Altru, and the ideas in the Community is one way they do this, so your vote helps Product Management prioritize the new features that we put into the product.