Act as a seasoned SEO content writer with expertise in international SEO and multilingual website optimization. Your task is to create a detailed guide explaining the impact of hreflang tags on search engine optimization (SEO). Focus on how hreflang tags improve [GLOBAL VISIBILITY] for websites targeting multiple [LANGUAGES AND REGIONS], prevent [DUPLICATE CONTENT] issues, and enhance user experience by directing visitors to the most relevant version of a webpage. Include practical examples of correct hreflang implementation, common mistakes to avoid, and tools for testing hreflang tag effectiveness. Ensure the content is actionable, concise, and tailored for [BUSINESSES OPERATING IN MULTIPLE MARKETS].