header='-d --header="User-Agent: Mozilla/5.0 (Windows NT 6.0) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.97 Safari/537.11"'
wget "$header" http://google.com -O index

wget: invalid option -- ' '
wget: invalid option -- '-'
wget: invalid option -- '-'
Usage: wget [OPTION]... [URL]...

header='--header=User-Agent: Mozilla/5.0 (Windows NT 6.0) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.97 Safari/537.11'
wget "$header" http://website.com -O index

args=(-d '--header=User-Agent: Mozilla/5.0 (Windows NT 6.0) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.97 Safari/537.11')
wget "${args[@]}" http://website.com -O index

wget $header http://website.com -O index

wget "$header" http://website.com -O index

someheader="-d --header='User-Agent: Mozilla/5.0 (Windows NT 6.0) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.97 Safari/537.11'"
wget "$someheader" http://website.com -O index