Revert "fix css button color"

This reverts commit fd2f453e6a2bcf095404a737ce5169bcac7d7db0.
Revert "Improve PDF display support"

This reverts commit d3741bb8444eb1fe6210ed5cb8cfc055c56f25a7.
Revert "Support PDF display"

This reverts commit 657f10073ec517bbc94d60b40a61104d0818a688.