This is a great script for checking what page types are causing bytes sent

SELECT
    EXTRACT_EXTENSION(cs-uri-stem) AS PageType,
    SUM(sc-bytes) as TotalBytesSent,
    TO_INT(MUL(PROPSUM(sc-bytes), 100.0)) AS PercentBytes
    INTO PagesWithLargestBytesSent.txt
FROM
    logs\iis\ex*.log
GROUP BY
    Pagetype
ORDER BY
    PercentBytes
DESC

Let say your CSS file had a lot of TotalBytesSent you might want to check these or if your pictures was high in % you might want to reduce the size/resolution etc.

//Anders