In Ubuntu Linux,some apps. only provide packages for 32-bit machine.And here explains how to install 32-bit packages on 64-bit machine.

For instance,I want to install linuxqq_v1.0.2-beta1_i386.deb on 64-bit ubuntu.Just run this command:

sudo dpkg -i --force-architecture linuxqq_v1.0.2-beta1_i386.deb

This will force to install 32-bit apps,although there’s a dpkg-warning says:package architecture (i386) does not match system (amd64).

If you want to remove  this  application you  have  to  force  it again .

sudo dpkg -r --force-architecture name