Add script in existing web page in order to remove the content

Ok, here is my problem. I made researches on Ebay with worldwild results, but I don't want to see results from China. Is it possible to add/load a script, this script will remove all tags containing "china" (actualy the "li" parent tag). I can develope the script but I don't how to insert it, and if it is possible. I hope that I am clear enough.