/%year%/%monthnum%/%day%/%postname%.html does changing the permalink to above gives SEO boast to wordpress blog ? thanks
Big time. Read about it here: http://www.johnchow.com/using-seo-friendly-urls-for-better-search-results/
Try not to make the URL too long. I just stick with /category/post-name or /post-name Just make sure you get it right before you start promoting the blog in the search engines, as having two cached versions of the same content could cause duplicate content issues.
If your using permalinks within Wordpress, create a .htaccess file by creating a text file and naming it .htaccess and uploading it to your server. Then make sure that it's editable and use the permalinks feature to create the URL you want. Because you've left the .htaccess file as editable WP will create the code for you.