Most Urgent: How to customize registration page

Hi,

First, you can read the documentation about the display customization using the HikaShop override system :
www.hikashop.com/support/support/documen...ize-the-display.html

You're using Joomla 3 with a bootstrap template, so you should edit the view "checkout | registration_bootstrap"

About the cart module customization, there is nothing to customize there, the best I see is to add some PHP code in order to display a Joomla message saying that the product "..." has been removed from the cart (and provide a link to re-add this product).
This kind of modification can be done using a custom plugin or by modifying the HikaShop core files.
I recommend the plugin because it allow you to update HikaShop without any problem (without loosing your modification).
www.hikashop.com/support/support/documen...umentation.html#cart

The trigger "onAfterCartUpdate" will be the most appropriate one (you have the product_id and the quantity, which is 0 when a product is removed).

Regards,

You need to develop a new hikashop plugin and implement in it the onAfterCartUpdate function as Jerome said.
Here is the Joomla documentation explaining how to create a plugin:
docs.joomla.org/J3.x:Creating_a_Plugin_for_Joomla