Icons and symbols are very important in graphic design. They can adjust perception of a web page, set the mood for the content, become an inevitable part of web design, make a webpage more comprehensive. It is not uncommon icons are used in web design as parts of the menus and other interactive elements.
Vector illustrations can be edited in many graphic programs, for example: Xara, Quark, PMView, Macromedia Freehand, Corel Draw, and sure All Adobe programs Photoshop, Indesign, Illustrator etc. can be used to open and edit vectors. As for me, I prefer to use Adobe Illustrator!