Add classes to images

gistfile1.txt

( function( window, document, undefined ) {

	var maybeAddClass = function( e, cn ) {
		var c = e.getAttribute( 'class' );
		if ( 0 == c.length ) {
			e.className += cn;
		}
		else if ( -1 == c.indexOf( cn ) ) {
			e.className += ' ' + cn;
		}
		return e;
	}

	var imgs, i, w;
	imgs = document.getElementById( 'content' ).getElementsByTagName( 'img' );

	for ( i = 0; i < imgs.length; i++ ) {
		if ( 860 <= imgs[i].width ) {
			imgs[i] = maybeAddClass( imgs[i], 'larger-than-860' );
		}
		else if ( 607 <= imgs[i].width ) {
			imgs[i] = maybeAddClass( imgs[i], 'larger-than-607' );
		}
		else if ( 300 <= imgs[i].width ) {
			imgs[i] = maybeAddClass( imgs[i], 'larger-than-300' );
		}

		/* Remove inline styles from image's caption wrapper element. */
		if ( 'A' == imgs[i].parentNode.tagName ) {
			var classAttr = String( imgs[i].parentNode.parentNode.getAttribute( 'class' ) );
			if ( -1 != classAttr.indexOf( 'wp-caption' ) ) {
				imgs[i].parentNode.parentNode.removeAttribute( 'style' );
			}
		}

		/* Add a class to images that have been resized in the editor. */
		if ( 'naturalWidth' in imgs[i] && imgs[i].naturalWidth != imgs[i].getAttribute( 'width' ) ) {
			imgs[i] = maybeAddClass( imgs[i], 'forced-dimensions' );
		}
		if ( 'naturalHeight' in imgs[i] && imgs[i].naturalHeight != imgs[i].getAttribute( 'height' ) ) {
			imgs[i] = maybeAddClass( imgs[i], 'forced-dimensions' );
		}
	}
} ) ( this, document );

Does anyone have thoughts on this javascript code? Just adding classes to certain images in the div with the id of "content". Feel free to yell at me about anything! Need help understanding best practices ... want to master javascript before 2012 ... or at least be completely comfortable with it! Thanks