How to display the product code only on the invoice preview

To display the product code only on the invoice preview (and not on the printout) you can hide it using a CSS code.
To achieve this, go to Settings> Account Settings> Print settings, and then at the bottom of the page, in the Customize print with CSS field, use the following CSS code:

​} 
@media print { 

.main_inv_table > thead > tr > th:nth-child(3), 
.main_inv_table > tbody > tr > td:nth-child(3) { 
display:none; 
} 
}

Note. The product code will not be shown on PDF or on the printout. However, when you provide the client with a preview of the invoice - the product number will be visible in the invoice HTML code