Many people would like to keep users on their site and in some situations you may find opening aggregator links in a new window accomplishes this. (Be warned, however, that this tactic is sometimes considered underhanded and is generally not accessible.) In order to have users open links in a new browser window instead of leaving your site you can either look at the External Link module or override the aggregator code in your template.php:
Find the function to override
First open aggregator.module in your favorite text editor. Then locate this function in the aggregator.module file:
<?php
function theme_aggregator_page_item($item) {
$source = '';
if ($item->ftitle && $item->fid) {
$source = l($item->ftitle, "aggregator/sources/$item->fid", array('class' => 'feed-item-source')) . ' -';
}
if (date('Ymd', $item->timestamp) == date('Ymd')) {
$source_date = t('%ago ago', array('%ago' => format_interval(time() - $item->timestamp)));
}
else {
$source_date = format_date($item->timestamp, 'custom', variable_get('date_format_medium', 'D, m/d/Y - H:i'));
}
$output .= "
\n";