Template Monster’s journey dates back to 2002. Since 2002 it has been providing in house built templates. There is definitely a lot of development since then and it has made its way to the list of best Templates marketplace.
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https://latestrags.com/template-monster-review-pretty-wordpress-templates-but-is-it-right-for-you/
Template Monster Review: Pretty WordPress Templates. But Is It Right for You??