Mark Zuckerberg ditched his hoodie for a more grown up, married look ... as he and Priscilla Chan strolled on a cobblestone road on the Amalfi Coast in Italy. 

It's the second leg of their honeymoon -- they just left Rome.

Good to see Mark smiling, in spite of the fact that his fortune sank from $20 billion to around $17 billion. 

For Zuck, the glass is always half full.

Mark Zuckerberg and Priscilla Chan blended with the crowd during their honeymoon in Rome -- as best as a gazillionaire can blend.

It looks like they didn't attract much attention -- in fact, they seem to go unnoticed by most people in the crowded restaurant in the middle of the famed city.

Italy is fitting, because Mark said "arrivederci" to around 3 billion bucks this week after his Facebook stock took a nosedive.

In a roundabout way ... Mark Zuckerberg saved Zsa Zsa Gabor and hubby Prince Frederic von Anhalt from foreclosure.

Zsa Zsa and von A-hole were slated to lose their mansion at month's end because of a $700,000 mortgage that was in default.

Von A-hole tells us ... in a last-ditch effort to save the homestead, he jumped on Facebook and begged his fans for help. Shockingly, his prayers were answered. Even more shocking, he has fans.

Someone stepped up and helped von A-hole secure a $1.5 million personal loan -- which he used to pay off the mortgage.

But there's a catch -- Von A-hole has ONE YEAR to pay back the loan ... a loan which we understand is secured by the house.

Tick, tock.

Mark Zuckerberg's freshly-minted wife, Priscilla Chan, evokes a lot of interest but not much action ... according to the shop where she bought her wedding dress.

Cate Malone, the owner of the Little White Dress shop in Denver, CO, tells us the store has been buzzing with curious customers who have been trying on the $4,700 Claire Pettibone gown Priscilla wore at her surprise wedding.

In fact ... traffic on the shop's website has gone up a whopping 680% since the nuptials.

But here's the bottom line -- it's a big fat zero, because no one has bought the dress.

Business has been bad all around this week in the world of Facebook.

Priscilla Chan is no dummy ... in fact, Mrs. Zuckerberg was voted "Class Genius" back in high school ... way before she decided to hook up with a guy who would change the world.

Chan -- now 27 years old -- received the title during her days at Quincy High School in Massachusetts back in 2003. Priscilla went on to Harvard, where she met Mark and the rest is, as they say ... on her Facebook timeline.

The lesson here: Stay in school, study hard and you too may land a billionaire.

If Mark Zuckerberg's new wife was expecting a MASSIVE diamond on her wedding ring ... she was SORELY disappointed.

Just days after the surprise wedding of the century, Priscilla Chan-Zuckerberg took her brand new ruby rock on the road ... flashing her piece during a lunch date with a friend in Palo Alto, CA yesterday.

According to reports, the $20 BILLION Facebook honcho -- who has a reputation for not caring about excessive displays of wealth -- designed the ring himself.

It's unclear how much the ring cost ... hopefully not much ... 'cause his Facebook stock has been sinking like Natalie Wood ever since it debuted on Friday.

So, we gotta ask ...

There's talk that Mark Zuckerberg timed his wedding to cut his new wife out of the $20 billion he raked in Friday, when Facebook went public, but it's simply not the case.

As you know, Mark married Priscilla Chan the day after his portfolio ballooned.  But here's the deal ... Under California law, if one person grows a business before marriage and sells it right at the time he or she gets hitched, the new spouse has no legal claim to the proceeds of the sale.

Disso Queen Laura Wasser, who reps almost every celeb in the throes of divorce including Britney Spears, Angelina Jolie and Maria Shriver, tells TMZ it's pretty simple:  "Facebook is a separate property asset of Mr. Zuckerberg.  It's like a painter who paints a painting prior to marriage and sells it shortly after marriage.  Any proceeds from the sale of the painting are the artist's separate property."

Now, if Facebook continues to increase in value during their marriage, Priscilla would have a 50% interest in proceeds from the growth.  But if today is any indication ... Priscilla shouldn't hold her breath -- the stock plummeted 10% today.

BTW, we don't know if Mark got Priscilla to sign a prenup.

Tough morning for The Zuck -- after a lackluster debut ... Facebook stock is sinking like a stone this morning ... down more than 11% from its opening price.

As of 7:32 AM PDT ... FB had fallen to $33.97 per share ... down $4.26 from its closing price on Friday.

According to MSN.com, the stock was down as much as 14% earlier in the morning.

FYI -- Facebook debuted at $38-per-share ... and many hoped it would explode. It didn't.

Of course, we're still a long way from the closing bell ... and a lot could happen -- good or bad.

Stay tuned ...

Mark Zuckerberg might have more money than the average man, but he has the same musical tastes as everyone else -- because TMZ has learned his wedding was bumping some serious Michael Jackson tracks all night long. 

A neighbor of the Facebook CEO tells TMZ ... they could hear the music coming from the wedding the entire time (as evidenced by our video where you can hear Billie Joe Armstrong singing from the street).

The neighbor tells TMZ there was plenty of upbeat music all night -- including Flo Rida, Bon Jovi and Janet Jackson. But the overwhelming favorite was the King of Pop himself, Michael Jackson. 

Status update: everyone loves MJ.

Billie Joe Armstrong performed a touching love song at the wedding of Facebook CEO Mark Zuckerberg yesterday -- which was captured gloriously in this video ... shot from outside the wedding and through some bushes and you can't actually SEE anyone. Ah, romance!

Zuckerberg and longtime girlfriend Priscilla Chan tied the knot yesterday and Zuckerberg's home in Palo Alto, CA. The couple had been dating for nine years.

Each had quite the busy week, nuptials aside -- Chan graduated from medical school at the University of California, San Francisco on Monday ... and Zuckerberg MADE A BILLION DOLLARS!!!!!

 

Facebook founder and CEO Mark Zuckerberg capped off a busy week by getting married today to longtime girlfriend Priscilla Chan.

The couple, who met at Harvard and have been together for nine years, tied the knot in a small ceremony at Zuckerberg's house in Palo Alto, Calif. 

Chan, 27, has been busy this week too -- she graduated from medical school at the University of California, San Francisco on Monday.

A company spokeswoman said the ring featuring "a very simple ruby" that Zuckerberg designed himself.

That lucky b***h.