You can submit your website to the mighty Joomla showcase by just registering on the showcase site. But before doing so please go through the Guidelines for Submission. Further before submitting you website or web blog to the Joomla showcase makes sure that you website isn’t already in the showcase because in some cases you or your fiend might have already submitted the same website in the Joomla directory.
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Only those websites which meets the guidelines will be appreciated and the rest will be rejected. The main objective of the showcase is to display the power and extensibility of Joomla. While submitting your website you can also add your site thumbnails (no logos) for enhancing your website display. Once your website is submitted, the same will be verified by the Joomla moderatos and thus it is recommendable to submit no more than 10 (Ten) websites each month, otherwise the moderators may take you as spammers.