WordPress (the most popular software used for blogs, including this one) is so “helpful”, it removes blank lines in your pages and posts — including ones you insert on purpose. If you insert a line break or a paragraph with nothing (or a non-breaking space) in it to force a blank line, WordPress will remove it the next time you edit the page or post.
To force a blank line, insert this bit o’ code in HTML view wherever you want a blank line:
<p><code><br/></code></p>