WGET problem downloading pdfs from website

I'm trying to download all of the pdfs and ppts from this website: http://mlss2011.comp.nus.edu.sg/index.php?n=Site.Slides

I do in Cygwin:

wget --no-parent -A.pdf,.pptx -r -l1 http://mlss2011.comp.nus.edu.sg/index.php?n=Site.Slides

but no files are downloaded.

What do I need to change in the above wget command for thi开发者_运维技巧s to work?

needed to use the -e robots=off code, so this worked

wget -e robots=off -A.pdf,.pptx -r -l1 http://mlss2011.comp.nus.edu.sg/index.php?n=Site.Slides

Also in general, use the --debug flag for more help.