I had problem when posting an article on blogspot. I was trying to show some sample html/xml code in that article. But I faced problems when I wrote the core html code. The problem was that the html code was rendering as html controls and breaking the post content. I tried many times and got frustration. Finally I searched in google for this problem and I got the below useful link.
If you follow the above link you will notice 2 textareas in which the first one is for input the html code and second one is for output of the changed html code which fits into the blogspot post and renders as expected.
Whoever wants to post the html code in blogger, please go to the link and paste your html code in first text box control and click the process button. Then you will notice the second textbox updated with the processed html code. Then copy the complete code from second text box and paste it in your blogspot post. It works not only in blogspot but also in all blogs which don't allow direct html code in posts.