An electronic device may have a housing in which a display is mounted. A gasket may be mounted in a groove between the display and housing. The gasket may contain an embedded stiffener. Corner brackets may be installed in the corners of the housing. The housing may have inner and outer concentric ribs. Recesses in the housing may be configured to receive the corner brackets. The recesses may be formed between the inner and outer concentric ribs. Gap filling structures such as a foam layer may be interposed between a rear housing wall and a display backlight unit. Display color variations may be corrected by using a backlight unit having an array of light-emitting diodes of different colors. An electrostatic discharge protection layer may be grounded to a housing using conductive tape. Black edge coatings and adhesive-based structures may block stray light. Camera window regions may be supported using adhesive.