Comment on Blix AdSense WordPress Theme by SEO Dave.
Without looking at the css my guess would be a plugin has broken the css coding, I see a link at the bottom of the footer about a Theme Tweaker, I’d first try disabling it and see if it’s the issue. If not disable all plugins and see if the problem still occurs.
Looks like what’s happening is the main content is too wide and is pushing the sidebar down the page. This can happen if the css code is changed and you’ve made a mistake or a plugin has added css coding that clashes with the themes styling.