Need CSS to Justify text for all posts

Hello All,

I wanted to justify text for all posts across my Blog Bloggerz Arena

Also,
If you see my posts,there is very little margin when a picture is added below H3 tag. Below H2 tag it appears just fine. And also text below h3 tag is just about. Its just picture below h3 which has little margin. What can be the exact cause? Here is an example.

http://www.bloggerzarena.com/top-6-online-jobs-without-investment/

Can someone help with it? I must admit I have very little knowledge about CSS.