In general, Google gives precedence to older site's in it's results. That is, if two identical sites existed, the older of the two would likely rank higher in the search engine results than other. This makes logical sense of course.
If a website has been up and running for some years it is likely that the webmaster cares enough about it to keep renewing it each year. Equally his visitors like the site enough to keep returning - thus making it worthwhile for the owner to continue working on it. Conversely spammers throwing up hundreds of por quality sites realise that their type of sites tend to be banned from the search engines quickly so these sites never last long. After all, why pay to renew a site if you can't get any visitors to it? And so this leads us to the mysteries of website aging. In short, when you launch a new website you will typically have to wait anything between 3 and 6 months for it to really start performing well in Google. Because of this, older domain names and sites have value purely in terms of their age.
Indeed, some internet marketers refer to "aging" a website like a bottle of wine, for best results. For new web masters this is often not a possibility but as your website empire expands you may want to consider this process for faster results. The technique is incredibly simple, and essentially involves planning ahead. You decide on the web site(s) you will likely be building in the next 3-6 month window and buy the domain names now.
You stick up a one page "holding site" - the sort that simply says "This site is coming soon" - and then get it indexed in Google. When it comes to the time to actually build the site you have a well-aged domain. Another tactic in the websitw aging arena is to register domains for longer periods of time for the very reasons discussed earlier. Some entrepreneurs have claimed that registering a domain for 2,3 or more even years rather than the standard 1 year will help to convince Google that you're in for the long haul and that you aren't planning any "funny business".
One final technique to discuss on this topic is that of buying existing sites or domains that have been registered in the past. Here's an example. Someone buys a domain, builds a website and markets it. They start generating links to the site buy eventually for whatever reason they stop paying attention to the site. You may well be able to convince this person to sell you their site - a pre-aged site - for next to nothing which you can then turn into your own site for an instant search engine advantage. Alternatively you can wait until the domain name expires and hope the owner doesn't bother renewing it.
You could then snap up this domain for the price of any other - but this time it is pre-aged. It's already in Google's index and has links pointing to it. So you bought yourself a considerable asset at a knockdown price.
Richard Adams has been teaching about ecommerce and online business since 2000 and has a free report for you on how to accept credit cards.