The issue in your code lies with the space between url and the opening parenthesis. In CSS, when specifying a URL for the background-image property, there should be no space between url and the opening parenthesis. Here's the corrected code:
div.logo_div {
height: 48px;
width: 356px;
background-image: url("../img/logo_small.png");
}
Make sure to remove the space between url and the opening parenthesis. This should allow the background image specified by the URL to display correctly within the logo_div element.
Also, ensure that the relative path "../img/logo_small.png" is correct and that the image file exists at that location relative to the CSS file or the HTML file where the CSS is applied.