[PageLab]

Considering the image you posted, we're talking about a fixed-layout ePUB here. In this case, you need to specify the viewport dimensions in the head of the XHTML file, as follows:

<meta name="viewport" content="width=738, height=983"></meta>

Don't specify the image size on the <img> tag itself, do it in the CSS. You also need to specify page dimensions in the CSS:

body {
    width: 783px;
    height: 983px;
}

img {
    position: absolute;
    height: 983px;
}