Find

// Output a function button in the selected language
function tep_image_button($image, $alt = '', $parameters = '') {
global $language;

return tep_image(DIR_WS_LANGUAGES . $language . '/images/buttons/' . $image, $alt, '', '', $parameters);
}

change into

// Output a function button in the selected language
function tep_image_button($image, $alt = '', $parameters = '') {
global $language;

return tep_image(DIR_WS_LANGUAGES . $language . '/images/buttons/' . $image, $alt, '', '', '' . $parameters . ' onmouseover="(src='' . tep_output_string(DIR_WS_LANGUAGES . $language . '/images/buttons/over/' . $image) . '')" onmouseout="(src='' . tep_output_string(DIR_WS_LANGUAGES . $language . '/images/buttons/' . $image) . '')"');
}

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