how to set up backgroung image in auto

hi i got a question i dont want to change all configuration i select custom style but i make another bg_7 and replaced the one has coming but i want to put the imagen in auto to fit the screen. and the heigh is because when i load another module the imagen stay in the same pixel was made and look very bad.




i dont now if is here

body {
font-size:<?php echo $mainFontSize; ?>px;
color:<?php echo $bodyText; ?>;
<?php if ($backgroundImage!="none") { ?>
background:<?php echo $backgroundColor; ?> url(<?php echo $template_path; ?>/images/bg_<?php echo $backgroundImage; ?>.jpg) top left no-repeat;
<?php }else{ ?>
background:<?php echo $backgroundColor; ?>;
<?php } ?>
}







please help me. thanks in advance

Try to use background-size:cover;

see : www.w3schools.com/cssref/css3_pr_background-size.asp