tools for GUI

Hi,
i am not sure whether i am posting the question in the right forum but i hope this is the right forum.
i am designing an interactive GIS application over the web. the application i am designing is proposed to be hosted on a website if it works out well.
in this GIS application, i need to design a GUI. this GUI allows the users to select files,choose colors for the maps etc etc.
the GUI has a set of icons. by clicking on these icons, a file select box etc is displayed to users. from the list of specified files, the user can select a file(eg;a map of a country). similarly the GUI has other features like the Windows file open dialog box etc. most of this interface is similar to the typical Windows GUI
can u suggest me if any free GUI toolkits are available that will help me in creating this interface.
thanks in advance