Kayak, the travel search engine, recently filed for an IPO, the latest in many milestones for the company.

Here's the most important lesson that every small business should learn from Kayak's success over the years: It doesn't necessarily matter if you're the first, fourth or tenth company or person to an idea. Execution -- how you actually run your business -- matters more than the initial idea.

If you do something better than everyone else, in a way that's actually helpful to your customers, you can be successful, even if you are just improving on someone else's existing idea.

This is especially for small businesses. Remember, every large company started small, too. And they were usually trying to compete with companies much larger in size, with more money and an established brand.

So, what did Kayak do better than everyone else, anyway? How can you apply this to your small business?

Kayak delivered travel search results clean and fast, a concept that its competitors apparently could not grasp.

Kayak was not the first site to search multiple airlines or to let you filter your search results. But it used new technology like AJAX to do it fast and elegantly. It was a breakthrough in quality and user experience. And for that reason, the second we found Kayak, it became the only travel search engine we used.

One of the ways that your business can win customers over from competitors -- even if you're doing the same thing -- is to be simpler and easier to use. Remember, you're one of many tools and services that a customer is going to use as part of their daily routine. If you can do something for the customer in a way that's faster, less of a nuisance and more efficient, you could win many fans.

Often that means starting with far fewer features or options than your competitors.

This actually benefits small businesses. They don't have to worry about losing business due to product simplification. In many cases, less is more and a simpler product can be more successful than the original, bulky product.

Kayak is hardly the only site that took an existing idea, improved on it by simplifying it, and ultimately came out on top. Consider Google Maps, which made MapQuest and Yahoo Maps look like a convoluted mess. And the iPhone versus the Palm Treo and Windows Mobile. And Facebook, versus Friendster and MySpace. And Google for search, versus prior search engines like Yahoo and Lycos.

They weren't the first -- far from it -- but they were superior and eventually took a lot of customers away from their competitors.

This isn't to say you will definitely be successful if you take an existing idea and try to do it better. And this isn't to say that that being first to an idea doesn't create huge market advantages.

But you shouldn't be afraid to try to improve on an old idea. Kayak wasn't, and now it's going public.