Understanding Internet addresses (URLs)

Each document and resource in the Internet is identified by a unique address that distinguishes it from other documents and resources. This address is also called Uniform Resource Locator (URL). In this section we'll discuss only addresses for web resources (http and https protocols) insomuch as to get sufficient understanding for ads and cookie blocking.

You may see the address of the document you browse currently in Address box in Internet Explorer Address Bar. When you move the mouse pointer over links on a page, you may see the address of the documents these links point to in Internet Explorer status bar; however, some sites do not allow this. All pictures (banners), popup windows and other page elements (resources) have their own addresses. Banner, popup and cookie blocking is based on their addresses so it is necessary to have basic understanding of web addresses.

The simplified web address structure is:

protocol://host/folder1/folder2/resource1?param1=value1&param2=value2

For example, this address:

http://somedomain.com/images/banners/ads.dll?ad=1222&lang=10

has following parts:

• http:// - protocol;

• somedomain.com - host;

• images, banners - folders;

• ads.dll - resource;

• ad, 1222 - the first parameter and its value;

• lang, 10 - the second parameter and its value.

These address parts are described further:

• protocol aka scheme - protocol (set of rules) used to retrieve a resource from the Internet. For web addresses, two protocols are widely used: http and https. http protocol is used for retrieval of insecure documents while https is used for secure documents;

• host - computer (host) name or its IP address from which a resource can be retrieved. These names are registered by site owners (and advertisers, too) within a special organization. This name usually identifies a site owner. An advertiser can have multiple host addresses registered but their number is usually limited. Due to this fact Ad Annihilator is able to identify resources that come from advertisers.
  The host part itself can consist of several parts separated by periods, e.g. http://ads.images.somedomain.com. The rightmost part is named top- or first-level domain, the next to the right is called second-level domain and so on. The domains to the left of the given domain are called subdomains as well. The number of top-level domains are restricted. For example, there are com, net, org, edu and other top-level domains. Site owners usually register their domains within the second level, e.g. http://advert.com. Some site owners are not primary advertisers by themselves but provide advertising services as their secondary activity. They often create third-level domains within their site name for serving ad content, for example, http://ads.somedomain.com, and even fourth- and so on level domains. Another way used to provide advertisements for the latter kind of advertisers is creating special folders for ad serving;

• folder - the hierarchical path to the resource on the host computer similar to file system path used to identify a location of the resource on the web server. It may contains several parts separated with slashes (/). The folder part in the address may be empty.
  As it was mentioned above for host part, some advertisers may use folders to designate a location from which their ad content comes, for example, http://somedomain.com/banner;

• resource - resource name, a name unique within the context specified by folder path that designates a web document or resource. Often this part designates not a static document or resource but a dynamic one generated by computer program on the web server. These programs are called CGI applications. The resource part may be empty, too.
  Sometimes resource part is used by advertises to serve advertisements from, e.g. http://somedomain.com/images/ads.aspx;

• parameters and their values - CGI applications often accept parameters to modify a resource that should be retrieved. Each parameter consists of its name used to distinguish it from other parameters and value that specifies the information carried by the parameter.
  If a CGI application is used to serve ad content, parameters often used for specification of which specific advertisement the application should be returned. Usually it is not required to pay attention to parameters of ad serving CGI applications as users usually want to filter all ads.

Understanding of Internet addresses is required for banner, popup and cookie filters understanding and for banner filter mask selection in Resource block, Resource unblock, Popup block and Popup unblock windows.