Are these Canon websites safe to download printer software?
You can check the signature/authenticity of a downloaded package installer (*.pkg) quickly yourself - independent of the shabby look of a website:

Open Terminal and enter pkgutil --check-signature. Then open the downloaded dmg image and drop the pkg onto the Terminal window and hit the enter key:

pkgutil --check-signature  /Volumes/PrinterDriver_MG8100\ series/PrinterDriver_MG8100\ series_161000.pkg 
Package "PrinterDriver_MG8100 series_161000.pkg":
   Status: signed by a certificate trusted by Mac OS X
   Certificate Chain:
    1. Developer ID Installer: Canon Inc.
       SHA1 fingerprint: 5B B8 FC D3 38 4C CA 03 CD B6 14 EE 1B 01 34 A7 75 A2 82 58
       -----------------------------------------------------------------------------
    2. Developer ID Certification Authority
       SHA1 fingerprint: 3B 16 6C 3B 7D C4 B7 51 C9 FE 2A FA B9 13 56 41 E3 88 E1 86
       -----------------------------------------------------------------------------
    3. Apple Root CA
       SHA1 fingerprint: 61 1E 5B 66 2C 59 3A 08 FF 58 D1 4A E2 24 52 D1 98 DF 6C 60




You get a more OS X GUI like approach by simply clicking the lock in the upper left after opening the pkg with Installer.app:





Valid SHA1 fingerprints for Apple updates are 

SHA1 FA 02 79 0F CE 9D 93 00 89 C8 C2 51 0B BC 50 B4 85 8E 6F BF
SHA1 9C 86 47 71 48 B3 D7 04 24 7A 3C 3F 56 EA 2D E5 94 4B 01 C2


for third party software signed by an Apple Certification Authority and some Apple updates also:

SHA1 3B 16 6C 3B 7D C4 B7 51 C9 FE 2A FA B9 13 56 41 E3 88 E1 86