If you want your wordpress URL appear as .html, you can do so by adding .html at the end of your existing wordpress permalink structure like this /%postname%.html
This will add .html to all URL; your wordpress URL becomes something like http://yourwebsite.com/wordpress-tips.html
If you set it up .html in permalinks section, wordpress will only add this extension to posts but not pages. Kep in mind this will not generate static .html files, just adds the .html extension to end of the URL.
I follow your instruction but i do not get any success………..