The majority of bloggers don't know any HTML - which is fine, you don't really need to know any since most blog engines work in the same way as Word does eg. if you want a word to be in bold, you just highlight it and click on the 'B' button. But there are times when a little HTML can be really useful.
For example, you want to include a link in your blog entry to another site, but you don't want that link to take people away from your site. You see, unless you place an additional command in the link 'mark up' code, anyone clicking on a link will leave your site and go to the new one. I am now going to teach you how to get round that in plain English and a few pictures to help!