In blogger/blogspot if you enter adsense or similar codes directly in post you will get the following error.
Your template could not be parsed as it is not well-formed. Please make sure all XML elements are closed properly.
Why so !
Because blogger/blogspot uses strict XHTML entities in its template.

This tool converts HTML and JavaScript advertisement codes into strict XHTML entities. As I said above, if you directly insert adsense ad codes in particular areas of blogger template, it will not work, you will get the error mentioned above. But once you convert it to XHTML entities by using this HTML Encoder Tool, then you can put your codes anywhere in blogger template.

This online tool is a HTML to XML parser (converter). Just put in your Adsense, Infolink, Chitika, Adbrite or any other HTML/Javascript code below and press Encode HTML Code, it will instantly convert the code and make it fully compatible with all kind of blogger templates.

Adsense Code Converter For Blogger / Blogspot Blogs :

Is there any Adsense Program Policy violation by using HTML Encoder Tool !
Not at all. Actually by converting your code, you are not modifying the adsense ad code in any way. Using this tool doesn’t breaks AdSense program policies. Once you apply the converted code, have a look at your HTML source, find your adsense code, match it with original code, you will find no change at all.