is helpful in visiting other websites in general. Thus by precisely controlling which scripts are run in each webpage viewed, the user retains full control over what happens on their computer CPU and computer screen. Methods One method of filtering is simply to block (or prevent auto play of) Flash animation or image loading or Microsoft Windows audio and video files. This can be done in most browsers easily and also improves security and privacy. This crude technological method is refined by numerous browser extensions. Every web browser handles this task differently, but, in general, one alters the options, preferences or application extensions to filter specific media types. An additional add-on is usually required to differentiate between ads and non-ads using the same technology, or between wanted and unwanted ads or behaviors. The more advanced ad-blocking filter software allows fine-grained control of advertisements through features such as blacklists, whitelists, and regular expression filters. Certain security features also have the effect of disabling some ads. Some antivirus software can act as an ad blocker. Filtering by intermediaries such as ISP providers or national governments is increasingly common. Browser integration As of 2015, many web browsers block unsolicited pop-up ads automatically. Current versions of Konqueror, Microsoft Edge, and Firefox also include content filtering support out-of-the-box. Content filtering can be added to Firefox, Chromium-based browsers, Opera, Safari, and other browsers with extensions such as AdBlock, Adblock Plus, and uBlock Origin, and a number of sources provide regularly updated filter lists. Adblock Plus is included in the freeware browser Maxthon from the People's Republic of China by default. Another method for filtering advertisements uses Cascading Style Sheets (CSS) rules to hide specific HTML and XHTML elements. This was once handled directly by a browser's user style sheet and custom CSS files. The CSS files employed regular expressions to describe a general advertisement profile. An example CSS selector from the once popular Floppy Moose (2003) style sheet is below. It simply hides anything with a link containing the characters "ad." A:link[HREF*="ad."] IMG Stylesheets are still used to block ads today. However they are almost always used by an ad-blocking extension that combines CSS with other techniques. AdBlock Plus syntax includes CSS selectors which they call "element hiding" rules. The newer uBlock origin even allows "cosmetic filters" which inject custom CSS declarations. Due to changes in advertising techniques, modern ad-blockers use more specific selectors, more frequently