Whatever you're searching for, put mac at the end of the name like: xxxx mac
Remember that if it's for mac it will for os9 or earlier have an extension like .sit or bin or im? (sorry can't remember) & for osx will be sit or dmg. SO in your search results press on the appropriate type. If you do a program search the press on sit or dmg for example & that will show only files compatible with mac.