max-width is the property used for limiting the width of the image to predefined value. So it will help to show small sized pictures to display in their original size while resizing the large-sized images into a predefined maximum width.
By doing this we can keep avoid any misalignment of web page due to large-sized images while keeping quality of small-sized images.
But this max-width property won't work in IE 6(Internet Explorer 6).
So we can use the below workaround to make it work in IE6 also. The below style will limit the image width to 300px.
width:expression(this.width > 300 ? "300px" : this.width);