Moreover, the constraint of a 240-pixel canvas taught a generation of developers that —a lesson later codified in responsive design’s meta viewport tag.
The phrase refers to a specialized, modified version of the classic Opera Mini web browser designed for feature phones and older Java-based (J2ME) mobile devices. This specific resolution (240x320 pixels) was the industry standard for "QVGA" screens common on legendary handsets from Nokia, Samsung, and Sony Ericsson.