A Photoshop script called HOIST converts PSD files into HTML and CSS code to transform designs into webpages. HOIST extracts information from PSD files and converts effects into equivalent HTML and CSS, combining it all into a static webpage design with no manual coding required. The script removes empty layers, creates separate folders for HTML and CSS files, links image files, and writes code for non-visible layers while assigning styles through classes to simplify scripting. HOIST is open source and supports Photoshop CS5+ on Mac OSX for automating webpage conversion from designs.