How to Block Flash
Blocking Flash prevents videos and some advertisements from loading automatically. This can be helpful for preventing you from seeing content you don't want to see. It can also be helpful in decreasing the amount of data your computer must transmit in order to load a page.
The FlashBlock plugin for Google Chrome replaces Flash plugins with a translucent box. This lets you know that there is Flash content on the page. If you want to view it, you simply click on the placeholder box and the Flash content will load.
The plugin also gives you options to add exceptions for certain sites. For example, you may want to disable it on YouTube, since nearly everything you do on YouTube involves Flash.