Why can I not install Firefox on my HTC G1/Dream with CyanogenMod 6.1?
Firefox also requires an ARMv7 processor. The HTC Dream/G1 is officially unsupported because its processor is ARMv6. See the supported/unsupported device list on the Mozilla wiki:


  These devices have ARMv6 processors and are not compatible with
  Firefox for Android:
  
  ...  
  
  
  HTC Dream (T-Mobile G1, Android Dev Phone 1)  
  
  
  ...