Why can't search engine crawl my website?

Please show me how to edit my website so that goole, yahoo as well as other search engine can crawl my website. I recently advertise my website on goole and yahoo, but I received a message: robot cannot crawl my website. Please show me how to fix it. Thanks for your help.

Would need your website address.

Also did they provide you with some code to add to site?

Thanks for your quick reply. I just find out a way to fix it. Thanks again.