For Excel / HTML / iCalendar files, you need to Right-Click Download → Save Link As / Download Linked File As then rename the file with the appropriate extension (.html / .ics / .xls).
If you install the latest Flash Player or Google Chrome, you will be able to just click Download instead. (These files are generated directly using your browser, so other browsers don't support downloading them like normal files yet.)
Image File (.jpg)
Note: For the above files, Code / Group / Room / Title / Week will be shown or hidden as you have selected in the timetable displayed.
Excel File (.xls) Using Excel 2003 XML (SpreadsheetML) format
iCalendar File (.ics) For import into Google Calendar, iCal, Outlook, etc.