I'm using the latest version of WordPress (3.5) and I am using an HTML5 responsive template.
The big problem is that when I write the content of the pages and the posts, although I use "Text" tab of the editor and type the HTML code directly, when I save the post the code is changed from HTML5 to XHTML.
For example, an image tag turns from
<img src="img.jpg" alt="alt text">
<img src="img.jpg" alt="alt text" />
How can this be avoided?