you are trying to download the homebrew browser, or you are trying to download other apps using the homebrew browser.
You can get the HBB and other apps from ModMii's download page 2, should be working if you are properly manually copying apps to your sd card, modmii isn't doing anything special there.
Also make sure you are getting apps from ModMii, wii.guide, or oscwii.org. If you got the HBB from a different source it may be outdated and trying to grab files from a dead server.