Okay, for you that have been familiar with wordpress, you probably already knew about the "More" tag. It's a concept of shortening each post that is shown on your main blog's page. It truncates some portion of the post, and only shows few first lines of the story.
Does it neccessary to do so? Well, if you have the habit to write long paragraph (not just for one post, but all your post) then your main page would looked so tiring to read. And that is one minus point you will get from your reader.
If you have decide that this tips as interesting, then here it is (it's very simple, though): How To Add the Blogger "Read More"
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