<div class="left"><img src="img/123.jpg"/></div>
<div class="left"><img src="img/345.jpg"/></div>
</div>
////////////////
var divs=ddd.getElementsByTagName("div")
divs[0].style.marginRight = "20px"
divs[1].style.marginLeft = "20px"
<div id="ddd"><div class="left"><img src="img/123.jpg"/></div>
<div class="left"><img src="img/345.jpg"/></div>
</div>
////////////////
var divs=ddd.getElementsByTagName("div")
divs[0].style.marginRight = "20px"
divs[1].style.marginLeft = "20px"
var body = document.getElementsByTagName('body')[0]body.style.margin = 0
body.style.padding = 0