Frequently HTML-documents are connected among themselves, they have references against each other. References can be both absolute, and relative. Both those and others have lacks. Absolute references can be too bulky and cease to work, if the lower document on hierarchy is moved. Relative references are easier for entering and updating, but also this connection breaks, if the senior document on hierarchy is moved. Both kinds of connections can be broken at carry of the document from one computer on another.

Frequently happens, that the user has loaded the big document on the machine and was disconnected from a network for its detailed studying. All references in a local copy of the document will cease to work. For their "reanimation" it is necessary to address again to the original document, which is taking place on the removed computer.

Fortunately, developers HTML have provided this problem and have added two tags, <BASE> and <LINK> which are included in heading that connection between documents was not broken.