You may have arrived at www.crawler.com for a variety of reasons, but most likely because you have elected to set www.crawler.com as your home page by selecting the "Make www.crawler.com my home page" checkbox during the Crawler Toolbar installation.
You could also have clicked on the "Yes" button, when this window appeared:
If you don't want www.crawler.com as your homepage, please see the "How do I reset my homepage to its previous settings?" FAQ for further instructions.