Visitors judge your site quickly

An article at Wired states,

"... researchers discovered that people could rate the visual appeal
of sites after seeing them for just one-twentieth of a second. These
judgments were not random, the researchers found -- sites that were
flashed up twice were given similar ratings both times."

So both content and general appearance are important. But remember, content is what will keep them coming back for more.

Also remember that viewers make a fast judgement about your site. A bad site is worse than non at all.

Read the full Wired article