If he does not leave the site to post that ad, it is only because of the unique offer on this site. That is, the site should be much better than the competition, that, despite the inconvenience, visitor did not leave him and would not go away to competitors. In fact, most users still prefer to competitors that do not use such methods. Animation, do not overlap other content, much better, but It often causes rejection. For many people, the continued movement on the screen can cause severe irritation, and if this is accompanied by music, the irritation is greatly increased. However, short of time change on the screen, taking place in response to user actions, most often cause a positive response. But for such a change is not always necessary to use Flash, much realized standard means of html and css, possibly with a small complement of JavScript. Not bad seen and a small animation when you first load the page, but it must cease when the visitor will proceed to read the information.
However, such an animation often go unnoticed, as the designer wants to be noticed creation absolutely all site visitors. The use of Flash technology also greatly increases the size of Web pages, which increases the download time. Unfortunately, not all users have broadband internet access, and visitors to the site using a regular modem, can be quite a lot. If huge Flash-animation is located on the main page, there is the probability that some visitors will leave him, and not waiting for the download. In addition, Flash is not conducive to search engine optimization. Although today, some search engines have announced to work with files Flash, the html they work much better.
On some sites, Flash-animation completely justified. If the site extends some useful information, and receives revenue from advertising, the site owners it is important to draw attention to this advertisement. Let Visitor distracted from reading the information, because it's advertising that money brings, and it needs to attract attention, and basic information only serves to attract visitors to the site. Likewise, the animation is useful on sites created the advertising campaign, as they are developed in much the same way as television advertising. If the site supports the business of a commercial organization, it is important information about the proposed products and services. Diversion of this information means the potential loss of customers, and hence loss of revenue. Although it is sometimes useful to draw attention to any particular product or service, but this is better achieved by other means, since the constant animation prevents the study of other texts, and more important a few snippets of a page rather than one. On Web sites, intended to support the sales of goods and services that are not recommended for use constantly changing images. Often better to do without Flash, but in some cases, you can animate the page load and response to user actions. Flash file size should not be too large, and the page should properly displayed and disabled support Flash. If you implement any ideas should first use the html and css. Next, you should try to avoid JavScript and only if unable to resolve the problem by other ways to use Flash.