Here's how to tell which one it is in a sentence:
* Verb (past participle): "The website was designed by a professional." Here, "designed" is part of the verb phrase "was designed."
* Adjective: "The designed website is user-friendly." Here, "designed" modifies the noun "website," describing its characteristic.
Let me know if you have a specific sentence in mind, and I can help you determine the part of speech for "designed"!