Some websites can disallow you to download its page by identifying that the user agent is not a browser.

So you can mask the user agent by using the -–user-agent options and show wget like a browser as shown below.

wget --user-agent="Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.3) Gecko/2008092416 Firefox/3.0.3" URL-TO-DOWNLOAD