Sketch has a nice little feature to help web designers in getting their designs from a static mockup in Sketch to real HTML.
If you select any number of elements in the canvas, you can then go to Edit › Copy CSS Attributes in the menu. Sketch will then create CSS declarations for the borders, fills, gradients, shadows and text styles used in the selected objects.
Sketch transfers its gradients to CSS gradients too. As the syntax for gradients is kinda hairy, this is a real time-saver. Transferring designs from Sketch to CSS is now very easy indeed.