Facebook's back at IPO levels. What's making investors so happy? Facebook's stock has had a rough time on the market since it went public in May, but the social network's shares have roared back over the past week. Shares briefly popped above the company's initial public offering price of $38 per share in early Wednesday trading for the first time since its debut, riding a wave of goodwill from earnings last week. Investors are happy because Facebook seems to have finally gotten a handle on what it identified as its two biggest problems headed into its public offering: a shift to mobile users and a persistent question about whether it had a good long-term strategy for desktop and mobile ads. In its latest report, Facebook showed a very strong position on mobile, with the number of monthly users increasing 51 percent and advertising on the smaller screens accounting for around $656 million of the company's $1.6 billion in ad revenue over the past three months. That's particularly impressive when you consider that, last year, Facebook made virtually nothing from mobile advertising. Facebook is pushing forward in its efforts to court advertisers to buy space on its network. In June, the company said that it was working to streamline its advertising products in response to feedback from its customers, who complained that figuring out how to reach a target audience on the site was too difficult. There's also been lots of chatter about the possibility that Facebook might introduce video ads on the site in the near future. The firm recently introduced the ability to film 15-second videos through its Instagram service - a length that many pointed out was ideal for advertisements. On Wednesday, a Bloomberg report citing unnamed "people familiar with the matter" said that Facebook may even be considering selling TV-style ads on its site for as much as $2.5 million per day. Efforts to wring money from ads on smaller screens have come with an larger push to make Facebook a "mobile-first" company, focusing developer energy on creating products that encourage users to use the network as they tap away at their smartphones and tablets. The company has said that it is enhancing its search function - making it easier to search through all the personal information on the site - which will available on mobile soon. That move could help make Facebook a search destination in cases where users are out looking for restaurants and want a friend's recommendation. The he company's adoption of Twitter-like hashtags to surface interesting conversations on the site could also help Facebook bump up its engagement. All this stands in sharp contrast to the Facebook of a year ago, when the company was trying to launch standalone mobile apps such as the self-destructing photo app Poke, causing the impression that the network was floundering for a way to reach its target audience. While the site still faces questions about whether it's in position to keep up its appeal to younger users, these latest numbers seem to have encouraged investors - for now - to believe that the company is learning to grow up, itself. Washington Post Co. chairman and chief executive Donald E. Graham is a member of Facebook's board of directors.