Preview doesn´t work well

Start by deactivating ALL plugins and switching to the twentytwelve theme to start troubleshooting.

Switch to the twentytwelve theme. See if that solves the problem. If so, start reversing your steps one by one to see what’s causing the problem.

I’m not sure what you mean. What theme are you using that isn’t working?

If it’s a theme-specific issue, you’ll need to ask WooThemes about it – as commercial themes aren’t supported here – partly because we don’t have access to them.

I’m not even clear on what the problem is – and since I don’t have Canvas, can’t reproduce it. Perhaps you can post a screenshot to your site or someplace else an include a link to it.

Might also just be the way that theme works with preview.