Flash as a multimedia platform was introduced by Adobe and gave developers the chance to make eye catching websites and animations. As an online tool its popularity grew quickly and browsers rushed to support it as a standard. Flash player could only be provided as a plugin and not run natively by browsers and this soon became an issue.
With content becoming more complex and detailed, Flash struggled to keep up with making its software lightweight for browsers. Webmasters and indeed users became sick of the now annoying constant animations put before them and even more so, the way it slowed down their browsing experience. A huge blow to Flash came when Steve Jobs of Apple famously decided not to support it on their iPhone, iPad and Mac devices, instead suggesting web developers come up with alternatives. These included building mobile specific sites and using the new HTML5 language instead. Flash continued without Apple and indeed will continue in to the future; however one must now consider it a legacy format.
With Apple publicly shunning Adobe and Flash, the HTML5 format began to gather pace. The successor to HTML4, HTML5 offers a format that natively supports nearly all multimedia tools required by developers. This has made the format far more lightweight than Flash could ever hope to be and works great on mobile devices due to its relatively low power consumption. Indeed heavyweights such as Apple, Twitter, Google and even Facebook have come out in their support of the format.
In its early days, differences in browsers meant the HTML5 experience could vary and was not quite up to standard. Developers now seem to have little or no problems making everything uniformly great across the board, something the end user will surely appreciate.
Flash is dead, and its true successor, HTML5, is here to stay. Make sure your website is designed with this in mind.