Most CMS's like Wordpress or Joomla make a large number of queries and calculations just to load up a single web-page. This puts strain on your server and ultimately makes your website load more slowly. Generally out of the box a CMS is pretty light, but as you customize it with pligins, new themes and features it can have a lot of queries and calculations to make on every load making it very very slow. I've seen some take 20 seconds to load even on dedicated servers. Ouch! Double ouch given that Google now looks at site speed. The best solution for this is to install a cache plugin, be careful though as these do have some flaws and can be difficult to set up. I know a lot of people who set them up only to find they did not correctly configure them (or they stopped working after a while) and their site was slow again.
Nice post dude it certainly helped me...............a lot i have a site build up by word press and Magento I will certainly install the cache plugin