Which element cannot be customized in stock templates?

The ability to edit HTML codes in stock templates is typically restricted because these templates are designed to provide a consistent user experience and to streamline the process for users who may not have extensive technical expertise. Stock templates come with predefined structures and styles that maintain brand consistency across an organization’s communications. Allowing users to alter HTML could compromise the integrity of these templates or introduce coding errors that affect layout and functionality.

On the other hand, adding custom images, creating responsive designs, and changing layout styles can generally be accommodated within stock templates. Users have the flexibility to personalize their communications by incorporating images that reflect their branding, adapting the templates to ensure they display well on any device, and modifying layout styles to suit specific content needs. These capabilities enhance the usability of the templates while ensuring that they remain accessible and cohesive for different user scenarios.