As we know that CSS stands for Cascading Style sheets and Flash is an entirely different thing. Both tools are used in web design and have their own significance individually. Flash is considered as the better option as far as features and facilities are concerned and flash has more options to offer to a website. Web designers have used style sheets in designs because of the features of CSS websites which were more search engine friendly, easy to modify, less costly to make and update, but flash gives a liberty to the web designer and also responsible for making a website more interactive.
Basically, CSS separates design from content. The user and search engines also get benefit from the cleanness of CSS design. The content is easily indexed by search engines and it is a user-friendly option. CSS is has been the easiest way to update your website. While editing your website with a separate style sheet the designer make huge changes within seconds. CSS carries the content in the original structure and you can optimize your website through this for a longer time.
Being more interactive flash allows you to include sound into your pages via mp3 and wav files. It also allows the designer to mix any multimedia file format to the site. Taking for instance bitmap image formats like GIF, JPEG, PNG, PCT and TIF. Flash allows the designer to put objects at any place they like in the website with any hassles. The features of flash include box model problems, discrepancy across browsers, z-indexes, and tables-in-tables-in-tables, any graphics piece or screen resolutions.