/* this is a variation on the basic document object constructor we have used up until now.                                                                                                                                                                                                                
Two functions are defined: getDocObj() and getStyleObj. The getDocObj() function creates the document object for the browser in use depending on whether it recognizes document.layers, document.all or document.getElementById(). The getStyleObj() function gets the style object of a document object.
                                                                                                                                                                                                                                                                                                         
To invoke each, use like this:                                                                                                                                                                                                                                                                           
                                                                                                                                                                                                                                                                                                         
variablename = eval(getDocObj(elementidvalue));                                                                                                                                                                                                                                                          
                                                                                                                                                                                                                                                                                                         
or                                                                                                                                                                                                                                                                                                       
                                                                                                                                                                                                                                                                                                         
variablename = eval(getStyleObj(elementidvalue));                                                                                                                                                                                                                                                       
                                                                                                                                                                                                                                                                                                        
Use this in conjunction with any cross-browser script where you must account for Netscape 4.x, IE 4.x and W3C DOM compliant browsers.                                                                                                                                                                   
                                                                                                                                                                                                                                                                                                        
*/                                                                                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                                                                                        
                                                                                                                                                                                                                                                                                                        
function getDocObj(elem,parent) {                                                                                                                                                                                                                                                                       
 if (document.layers) {                                                                                                                                                                                                                                                                                 
 if (parent) {                                                                                                                                                                                                                                                                                          
 return "document."+parent+".document."+elem;                                                                                                                                                                                                                                                           
 }                                                                                                                                                                                                                                                                                                      
 else {                                                                                                                                                                                                                                                                                                 
 return "document."+elem;                                                                                                                                                                                                                                                                               
 }                                                                                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                                                                                        
 }                                                                                                                                                                                                                                                                                                      
 else if (document.all) {                                                                                                                                                                                                                                                                               
 return "document.all."+elem;                                                                                                                                                                                                                                                                           
 }                                                                                                                                                                                                                                                                                                      
 else if (document.getElementById) {                                                                                                                                                                                                                                                                    
 return "document.getElementById('"+elem+"')";                                                                                                                                                                                                                                                          
 }                                                                                                                                                                                                                                                                                                      
}                                                                                                                                                                                                                                                                                                       
                                                                                                                                                                                                                                                                                                        
                                                                                                                                                                                                                                                                                                        
function getStyleObj(elem,parent) {                                                                                                                                                                                                                                                                     
 if (document.layers) {                                                                                                                                                                                                                                                                                 
 if (parent) {                                                                                                                                                                                                                                                                                          
 return "document."+parent+".document."+elem;                                                                                                                                                                                                                                                           
 }                                                                                                                                                                                                                                                                                                      
 else {                                                                                                                                                                                                                                                                                                 
 return "document."+elem + ".style";                                                                                                                                                                                                                                                                    
 }                                                                                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                                                                                        
 }                                                                                                                                                                                                                                                                                                      
 else if (document.all) {                                                                                                                                                                                                                                                                               
 return "document.all."+elem + ".style";                                                                                                                                                                                                                                                                
 }                                                                                                                                                                                                                                                                                                      
 else if (document.getElementById) {                                                                                                                                                                                                                                                                    
 return "document.getElementById('"+elem+"').style";                                                                                                                                                                                                                                                    
                                                                                                                                                                                                                                                                                                        
 }                                                                                                                                                                                                                                                                                                      
}