Joomla - Improve loading time, yslow rating, page speed

My Website is [login to view URL] I need to improve page speed and loading time. According to google webmster: Performance overview On average, pages in your site take 10.1 seconds to load (updated on Jun 22, 2010). This is slower than 94% of sites. These estimates are of low accuracy (fewer than 100 data points). The chart below shows how your site's average page load time has changed over the last few months. For your reference, it also shows the 20th percentile value across all sites, separating slow and fast load times. My page speed rating is 73/100