WIP list of f/e dev quirks that designers sometimes don't know

design.gotchas.txt

Font availability
Text kerning
Fonts sized in sensible units (not pt)
Including extra fonts/variants for very small amounts of content
Shadows that need to be programmatic being added to non-square things
Underlines being thicker than one pixel (on things that for whatever reason can't be given borders)
Spacing of underlines (as above)
Impossible z-orders
Gradient masks on things that can't be faked with image overlays
Matching heights of dynamically sized elements
Vertically centering stuff (argh)
Arbitrary line breaks in paragraph text that change between desktop/mobile
When designing mobile elements, using different images / different crops in content instead of scaled versions of desktop content (arrrrrrrgh)
If the design implies a certain amount of content, what happens when we don't have that much content? (often an issue in progressive campaigns)
Custom like buttons
Like buttons being arranged in odd ways (constraints of iframes), variable widths etc
Arbitrary re-ordering/nesting/truncating of content between desktop and mobile
2GB PSDs, nuff said
What do designs that go right to the edges of a canvas imply? What happens at other sizes? (various responsive possibilities)
Backgrounds on arbitrary-length multi-line text content