Search Engine Optimization (SEO) is a very complicated method in which all steps relate each other. Even a single little mistake can make your website ranking move down or a single intelligent technique take you to the top search engine placement. It is very difficult to understand logic of search engines as there are no terms or surety that you will get first rank on first page of any search engine, even major search engine such as Google, MSN and Yahoo can not give guarantee for top ranking.
With well design website as well as properly optimized site you also need to consider it is a SEO friendly source code. Your source code need to be validate using W3C validator (A website that lets you know international norms for standardize source code.) You can check your website in W3C validator, it shows numbers of errors with line no and error messages. For rectifying these errors you need professional and experienced programmer or person who can solve these errors. For any html based sites you need to validate for html and CSS using W3C validation.
It is essential to validate your website as it is also one of the important factor that search engine consider while preparing search engine result pages. By validating your website using W3C validator the chances to open your site can increase in any type of browser without an error.