San Francisco ( CNN ) -- iSad . That was the reaction of many as millions took to the web with the news of the death of 56-year-old Steve Jobs . Facebook and Twitter messages were filled with links and anecdotes about the impact technology -- and more specifically , Apple -- had on users ' lives . Apple invited people to email their thoughts , memories and condolences after announcing Jobs ' death Wednesday , saying the company lost a `` visionary and creative genius and the world has lost an amazing human being . '' CNN 's iReport is also collecting reactions . Jobs ' death jolted a generation that has never known a world without a cellular phone , and it elicited reactions from those who watched Apple grow from a Silicon Valley garage startup in 1976 to today 's leading tech company . `` RIP , Steve Jobs , '' read many Facebook messages . Still others invoked the visionary 's signature stage pitch , `` And one more thing ... Thank you . '' Many tweeted simply : iSad or iHeaven . `` Oh my God , dad . Steve Jobs has died . He 's my generation 's Walt Disney , '' 20-year-old Lauren Harrington of Atlanta told her father upon learning Wednesday night that Jobs had died . Celebrities , corporate executives and politicians , including President Barack Obama , paid tribute to Jobs . `` Our parents had JFK , we had Steve Jobs . Edison gave us electricity , Jobs gave us the Jetsons in real life , '' tweeted director and actor Kevin Smith . `` We lost an icon today . Mourn him . '' Actor Ashton Kutcher tweeted : `` Sending love & light to everyone @ Apple & the entire Jobs family . Today we lost a Giant who will be missed even by those who did n't know him . I never thought I could be so busted up about the loss of someone I never met . '' Obama hailed Jobs as one of America 's greatest innovators , a man `` brave enough to think differently , bold enough to believe he could change the world , and talented enough to do it . '' `` The world has lost a visionary . And there may be no greater tribute to Steve 's success than the fact that much of the world learned of his passing on a device he invented , '' Obama said in a statement released Wednesday . Obama , an avowed BlackBerry fan , revealed this week to ABC 's George Stephanopoulos that Jobs personally gave him an advanced copy of the iPad 2 . House Majority Leader Rep. Eric Cantor ( R-Virginia ) tweeted : `` There is not a day that goes by , and often not an hour , that a Steve Jobs ' invention does not better my family 's life . Thank you Steve . '' The flood of messages slowed Twitter to a crawl at times or produced error messages saying the site was over capacity . On the social networking sites , many quoted from Jobs ' heartfelt commencement address at Stanford University in 2005 , where he first detailed his battle with pancreatic cancer . Actor Hill Harper , paraphrasing the speech , tweeted : `` Do what you believe is great work . And the only way to do great work is to love what you do ! ... Do n't settle . '' Apple flew the flags at its Cupertino , California , office at half-staff , and an impromptu memorial sprang up at the venue as people arrived with flowers , letters and mementos , CNN affiliates reported . Several employees tweeted messages containing only the Apple logo . The many websites devoted to Apple rumors and products placed large banners in memory of the company 's co-founder . The alternative-culture blog Boing Boing revamped its design in honor of Jobs to resemble retro Macintosh software . Wired painted its front page black , with a shadowed picture of Steve Jobs in the center . Google 's co-founders posted statements about Jobs ' importance to them personally and to the industry , and underneath the search box on Google.com , the company added : `` Steve Jobs , 1955 - 2011 . '' Research in Motion , from its BlackBerry Twitter account , called Jobs `` a great visionary and respected competitor . '' Microsoft 's Bill Gates , who once worked with Jobs and later competed against him in the mobile world , said on his Twitter account : `` For those of us lucky enough to get to work with Steve , it 's been an insanely great honor . I will miss Steve immensely , '' â€ ” Bill Gates . And two men , whose social networking sites gained in popularity thanks in part to Jobs ' mobile-computing revolution , paid their respects to Apple 's mogul . In a message , Facebook founder , Mark Zuckerberg said : `` Steve , thank you for a being a mentor and a friend . Thanks for showing that what you build can change the world . I will miss you . '' Twitter co-founder Jack Dorsey wrote simply : `` Thank you . '' CNN 's Mark Milian , Douglas Hyde , Ed Payne , Chelsea J. Carter and Kevin Bohn contributed to this report .
Facebook and Twitter users post `` RIP , Steve Jobs '' Apple is inviting people to email their memories and condolences . Flags are flying at half-staff at Apple 's headquarters in Cupertino , California . The many websites devoted to Apple rumors and products place large banners in memory of the company 's co-founder .