In chrome's Developer tool, the blue vertical line labeled "DOMContent event fired", and the red line labed "load event fired". Does "DOMContent event fired" means the browser begin to execute the inline javascript? And "load event fired" means it fire "onload" event?
"DOMContent Event" is from webkit (which chrome relies on) and is equivelant to DOMContentLoaded msdn mdn.
The DOMContentLoaded event fires when parsing of the current page is complete; the load (onload) event fires when all files have finished loading from all resources, including ads and images. DOMContentLoaded is a great event to use to hookup UI functionality to complex web pages.
See the demo here, related question.