MSN commands almost 15% of all searches although some sources believe that the figure is somewhat less than this. It does however have a loyal audience which is unique to it. This fact is often ignored by many SEO specialists who tend to lean towards Google or Yahoo!
But if a serious SEO campaign is planned then MSN cannot be ignored as it has less competition to cope with. Rankings will be higher using less popular keywords because of this fact. Traffic to a site may benefit from enough visitors to make it a worthwhile option.
The same common rules when optimizing with MSN as with other search engines, in order to gain a higher rank with a search engine and it can be reasoned that if a site ranks well in either Google or Yahoo!, it will rank just as well in MSN. But the opposite, sadly is not the case making it vital to keep an eye on Google ranking at all times. The reason that it does not work both ways is that MSN algorithm is not the same, so even when the web pages are the same in the index, the search results may be very different. The only way to optimize for MSN is to create a spiderable site, much as one would for any other search engine, without this the game is lost from the very off.
There has been much debate about the MSN algorithm and it is clear that it lacks the sophistication of the other two major search engines. Many SEO specialists believe that is too far behind its competitors. The solution to the problem is not quite as straight forward as it appears to be if considering using the same tactics as Google did a few years ago to solve the problem.
MSN relies on metatags, and they do this a lot. However, other search engines no longer rely this much on them. Metatags allow SEO specialists the chance of manipulating search results and this is believed to be one of the reasons why MSN produces such inaccurate ones.
Another important difference between MSN and the other search engines is the way they use keywords. Keywords are just as important to MSN, but on page factors are dominating while off page factors such as backlinks are considered of less importance. It is a fair bet that this will all change in the future.
MSN relies heavily on the use of keywords and it is therefore easy to dupe MSN with inflated keyword density or even add them in domain names but this is not advisable as it may lead to Google banning a site. One option is to have separate pages for both but it is definitely worth considering whether it is worth the effort. There is also the risk of duplicate content penalties.
The only solution is to optimize wisely and get good rankings in all of the search engines at the same time without compromising any of them when doing so. Remember that metatags are important to MSN but not with the other search engines and always keep in mind that if they are well written they will not upset Google because if they do then Google may ban the site altogether.