Ask HN: First impressions on website - do they help?

So, i am currently writing something up for a college class. Problem is everything is hypothetical. I need some proof. I believe a first impression on a website is imperative so that people actually use it and in my case, buy your product or services as well.

Basically I'm wondering has there been any studies that shows how a better web design will increase revenue for any kind of services? I don't just mean selling products like a T-shirt, but labor services as well.

If someone wanted their computer fixed and searched for companies that can do so, will a first impression on the website help them make their decision to use your company? Are there any studies like this? White papers maybe?

Only thing i really found was this: http://www.websiteoptimization.com/speed/tweak/blink/

Thanks!