I am undecided whether to use a Content Manangement System ( wordpress, drupal, joomla ) to build my own classified ads website like olx.com or craiglsit. Is it good to make a it using a CMS Or should I just hard code it on my own? assuming I have good programming skills.
The best is to see which achieve the most of what you want out-of-the-box, which reduces how much you have to tweak / code.
Wordpress is more for a blog so avoid that one. Joomla provides a good framework, but would require quite a lot of coding to extend.
A quick google says that classified ads-specific Content Management Systems do exist, eg http://www.opensourcecms.com/scripts/details.php?scriptid=345 Personally, I'd look into these.