The simple answer is: Type your query into the text box, then click on the [SEARCH] button and see if it works. If it doesn't work for you, use the [Alt. search] (alternate search) button instead. Then continue to use the same button for future searches.
Quick explanation: The [SEARCH] button displays results more conveniently, but it doesn't work with all browsers. The [Alt. search] button is there for people who cannot use the [SEARCH] button because it doesn't work with their browser. Both buttons search the same pages and give the same results, but the results are displayed differently.