Hello,
That popup is from the legacy add to cart system and it uses a Joomla squeezebox popup.
I highly recommend you to switch on the new cart system and use the "cart notify" plugin. It can display a notification tooltip or use a popup (based on vex).
www.hikashop.com/home/blog/367-hikashop-3-0-out.html#cart
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.