????自1999年瘋狂的互聯網熱潮至今已經15年了。伴隨著這之前幾年第一次互聯網熱潮的是過度熱捧的首次公開募股，這陣熱潮在持續一段時間后達到了頂峰。當然，它垮掉的速度要更快。

????如今，那個時代的記憶仍然揮之不去——奢華的天臺聚會，迅猛的首次公開募股和大量財富的創造（至少是紙面上的）——讓人感覺既傳奇又古怪。隨著Twitter的市場估值達到收入的70倍，以及科技中心的成本不斷攀升，關于另一個非理性繁榮的時代是否即將到來、抑或已經到來的爭論日趨熱烈。

????正如繁榮終有蕭條的一天，蕭條中也總會有幸存者。20世紀90年代末炙手可熱的初創公司中，仍有許多至今仍然生機勃勃，尤其是在互聯網【例如阿卡邁（Akamai）、瞻博網絡（Juniper）】、商業軟件【例如紅帽（RedHat）】和消費者網絡（例如Angie's List、Shutterfly）等領域。

????更引人注目的是，第一代網絡初創公司中的老手們不僅僅成功地存活下來，而且成為擁有百億或千億市值的大型品牌。無論互聯網行業會不會迎來下一次繁榮和蕭條，就如何建立一家經久不衰的初創公司而言，下面這五家公司都給人們上了一課。

????亞馬遜（Amazon）：無論如何，堅持愿景，不過同時也要根據數據來調整愿景。杰夫?貝佐斯寫給股東的年度致信多年來一直沒有什么變化。1997年，他表示亞馬遜會從長遠的角度為股東創造價值。為了達到這個目標，他將“延伸、鞏固我們目前的市場領先地位”，同時“堅持以顧客為本。”

????即便在蕭條期，亞馬遜也堅持了這兩點。在公司對最初愿景的堅持下，它的長期股東獲得了回報，亞馬遜的市值如今已經高達1850億美元。亞馬遜堅定卻不頑固。它不懈地追蹤顧客的數據，了解他們如何使用網站，什么能讓他們產生共鳴。借此，亞馬遜得以實現了擴張，同時提高了長期目標。亞馬遜對顧客的關注從未間斷，或許比起對自己的了解，他們對顧客的了解還要更勝一籌。

????奈飛（Netflix）：服務于一個不會消失、卻可能會隨著時間而變的需求。與貝佐斯一樣，里德?哈斯廷斯有著長遠的目標。他在2009年告訴《財富》：“（人們）出現疼痛時，你會想著扮演阿司匹林，而不是維生素。阿司匹林可以切實解決一些人的特定問題，而維生素則是個大體上‘可有可無’的市場。”

????奈飛也許不會治愈任何疼痛，它更像是在給人撓癢。不過人們的這一種癢永遠不會消失，那就是：用較低的價格、簡單的方式來觀看電影和電視。即便在奈飛統治了DVD租賃市場時，哈斯廷斯也有計劃：一旦寬帶網變得足夠快速和便宜，就開展流媒體視頻服務。

????與此同時，奈飛也證明自己可以靈活地滿足用戶需求。這家公司很早就開始明智地從賺取碟片租借費轉向更流行的每月訂閱費。最近，哈斯廷斯將業務擴展到了原創內容，增加訂閱量。盡管懷疑者認為這個舉措的代價過于昂貴。

????It's now been 15 years since 1999, a year that has since become synonymous with crazy Internet excess. The first Internet boom began several years earlier with an overhyped IPO and took a while to reach its febrile climax. Of course, it all crashed down much more quickly.

????Today, the lingering memories of the time -- extravagant rooftop parties, metoric IPOs, and massive wealth creation (at least on paper) -- feel at once legendary and quaint. With Twitter trading at 70 times revenue and costs of living rising in tech centers, the debate rages on over whether another period of irrational exuberance is nigh, if not already upon us.

????Just as every boom must have its bust, every bust will see its share of survivors. Many of the hot startups of the late 1990s are still alive and kicking, especially in networking (Akamai (AKAM), Juniper (JNPR)), business software (RedHat (RHAT)), and the consumer web (Angie's List (ANGI), Shutterfly (SFLY)).

????More notably, other veterans of the first generation of web startups have not only survived, they continue to be big online brands with 11-or 12-digit market caps. Whether the Internet industry is heading for another boom and bust, these five companies offer lessons on how to build a startup with the power to endure.

????-Amazon (AMZN):Stick to your vision no matter what, but fine-tune it with data. Jeff Bezos's annual letters to shareholders haven't changed much over the years. In 1997, he said Amazon would build shareholder value over the long term. But to do this he would "extend and solidify our current market leadership position" and "focus relentlessly on our customers."

????Even through the bust, Amazon did just that. Long-term shareholders have rewarded this stubborn adherence to an original vision with a $185 billion market value. But Amazon wasn't too stubborn. It obsessively tracked data on shoppers, how they used the site, what resonated with them to expand and enhance its long-term goal. The focus was so relentless, Amazon may know its customers better than they know themselves.

????-Netflix (NFLX):Serve a need that won't go away, but may change with times. Like Bezos, Reed Hastings had a long-term goal. "When there's an ache, you want to be like aspirin, not vitamins," he told Fortune in 2009. "Aspirin solves a very particular problem someone has, whereas vitamins are a general 'nice to have' market."

????Netflix may not cure any aches; it's more like it scratches an itch. But it's an itch that never goes away. Watch movies and TVs in a low-cost, simple way. Even when Netflix was dominating in DVD rentals, however, Hastings had plans for a streaming-video service once broadband was fast and cheap enough.

????At the same time, Netflix has shown it can nimbly adapt to its users' demands. The company made an early -- and shrewd -- shift from a by-the-disc rental fee to a monthly subscription that was more popular. More recently, Hastings branched into original content to increase subscriptions at a time when skeptics questioned whether a move would be too costly.