How can I know an icon will relay the same meaning across all cultures?

I work for a multinational company with websites in about 40 countries. There is a mix of European, Asian, Pan Pacific, North and South American countries we serve. I have been asked to design a common header to be used for all the sites. Language length aside, I do not want to make the mistake of thinking a North American best practice is the same as an Asian best practice, or a Brazilian best practice. Is there any examples of issues I should be aware of? Is a magnifying glass icon next to a text box recognized my most countries as a search? Is there a website that discusses this topic?