Tesla and SpaceX CEO Elon Musk has officially relaunched the mysterious website X.com, a domain he recently bought back from PayPal, on Friday (14 July). Earlier this week, Musk repurchased the defunct domain name from his former employer for an unknown sum for "sentimental" reasons.

Musk previously owned X.com back in the late 1990s when it served as the platform for his financial services startup that merged with a money transfer service called Confinity in 2000 and eventually went on to become PayPal. Musk left the company after a year, but later made $165m (£127m) for his shares when eBay acquired the company in 2002. However, he lost ownership of the X.com domain when he left.

"Thanks PayPal for allowing me to buy back X.com!" Musk tweeted on Tuesday. "No plans right now, but it has great sentimental value to me."

Musk did not reveal how much he bought the domain for.

Now that X.com is live, Musk has yet to reveal his plans for the website. As of now, the website just features a single letter "X".

"Excited to announce the launch of x.com!" Musk tweeted on Friday. "It's a little verbose right now, but that will be fixed tomorrow." A quick glance through the site's source code does not seem to reveal any hidden messages - just some simple HTML code.

"The source code for @elonmusk x.com is so sophisticated, so simple, brilliant. I'm not surprised," one Twitter user wrote.

"Small thing (very small), but I made it this way for those who care and understand. Source and appearance are the same," Musk replied.

The launch of the mysterious site has already fueled speculation that Musk could be announcing yet another innovative project. However, some have speculated that it could just be a landing page for his current businesses and ventures.

Earlier this year, he launched a tunnel boring business called The Boring Company and announced Neuralink, a venture working on neural lace technology to link the human brain with computers.