wepixel

Problem resolved after added below in css:

a.node {
display:block;
margin:-20px 0 0 20px;
}

a.nodeSel {
display:block;
margin:-20px 0 0 20px;
}

Idea taken from following post:
http://ww.wp.xz.cn/support/topic/plugin-wp-dtree-wordtext-wrap?replies=3