window.onload = function(){}; works, but as you might have noticed, it allows you to specify only 1 listener.

I'd say the better/newer way of doing this would be to use a framework, or to just to use a simple implementation of the native addEventListener and attachEvent (for IE) methods, which allows you to remove the listeners for the events as well.

Here's a cross-browser implementation:

// Cross-browser implementation of element.addEventListener()

function listen(evnt, elem, func) {

    if (elem.addEventListener)  // W3C DOM

        elem.addEventListener(evnt,func,false);

    else if (elem.attachEvent) { // IE DOM

         var r = elem.attachEvent(on+evnt, func);

         return r;

    }

    else window.alert('I'm sorry Dave, I'm afraid I can't do that.');

}



// Use: listen(event name, elem, func);

For the window.onload case use: listen(load, window, function() { });

EDIT I'd like to expand my answer by adding precious information that was pointed by others.

This is about the DOMContentLoaded (Mozilla, Opera and webkit nightlies currently support this) and the onreadystatechange (for IE) events which can be applied to the document object to understand when the document is available to be manipulated (without waiting for all the images/stylesheets etc.. to be loaded).

There are a lot of hacky implementations for cross-browsers support of this, so I strongly suggest to use a framework for this feature.