Researchers in Ottawa found that people decide whether they like the look of a web page in about a twentieth of a second, and that given ten times as long they come to almost the same verdict.
That first look is a promise about your work, so it should match your work, no better and no worse. Better, and you're writing a check your shop can't cash. Worse, and you're losing customers you never get to meet. Piece four of ten.
The whole talk, as video and as audio: https://markheinz.com/notes/the-whole-picture