A website's own search engine is fundamental to helping customers find products, make purchases, and have a positive shopping experience.

Speaking at an ecommerce conference in Brazil, Ed Huffman, vice president of global sales and business development for SLI Systems, a site search provider, told his audience that 43 percent of site visitors use search to navigate and find products. Separately, Mahmood Ahmad of FindWise, a site-search consulting firm, estimated that the number of visitors using site search was really about 50 percent.

If 43 percent or 50 percent or even 25 percent of an online retailer's audience is using site search to locate products, then it is clear that site search can have a significant impact on sales. Designing an ecommerce site to both encourage search and offer great search results may help merchants sell more. In fact, Huffman also noted that customers using site search might convert at a higher rate than their non-search peers.

So what sort of design choices makes an online retail site more search-centric? Here are four suggestions.

Make Search Fields Large, Readable

Usability guru Jacob Nielsen writing on his web usability blog, Alertbox, once said that “search is the user's lifeline for mastering complex websites.”

If search were a lifeline, meant to save site surfers from a poor shopping experience, online retailers would be wise not to hide search boxes, but rather make them an important part of each page's layout.

Amazon, which is, perhaps, the most recognizable online merchant in the world, includes its search box at the top of each page, positioning it to maximize visibility.

In a similar way, Barnes & Noble has a large, clearly defined search box at the top of its page.

A third example making search fields large and very readable can be found at Cafe Press, the retailer of custom t-shirts.

Suggest Search Terms

SLI's Hoffman said that about a third of site search users take advantage of search suggestions.

These users are twice as likely to make a purchase, and, also according to Hoffman, likely to purchase more, boosting average order value some 17 percent.

Good search suggestions should appear below the actual search field, right in line with the term being sought. Consider using a plan, readable font and making a clear distinction between what the user is typing and the search suggestions.

Search suggestions do not have to be limited to trying to match a word. For example, Apple offers both word suggestions and product suggestions in its search field hints.