用ASP+CSS实现随机背景

ASP--来自ASP101

以下是引用片段：
Const IMGS_DIR = "/images" 
'设定图片文件夹的地址，随机显示该文件夹内任一张图片 
Dim objFSO, objFolderObject, objFileCollection, objFile 
Dim intFileNumberToUse, intFileLooper 
Dim objImageFileToUse 
Dim strImageSrcText 
Set objFSO = Server.CreateObject("Scripting.FileSystemObject") 
Set objFolderObject = objFSO.GetFolder(Server.MapPath(IMGS_DIR)) 
Set objFSO = Nothing 
Set objFileCollection = objFolderObject.Files 
Set objFolderObject = Nothing 
Randomize() 
intFileNumberToUse = Int(objFileCollection.Count * Rnd) + 1 
intFileLooper = 1 
For Each objFile in objFileCollection 
If intFileLooper = intFileNumberToUse Then 
Set objImageFileToUse = objFile 
Exit For 
End If 
intFileLooper = intFileLooper + 1 
Next 
Set objFileCollection = Nothing 
strImageSrcText = IMGS_DIR & objImageFileToUse.Name 
Set objImageFileToUse = Nothing

CSS

以下是引用片段：
#pic{ 
width: 400px; 
height: 300px; 
background: url() no-repeat; 
margin: 2em auto; 
}

上面代码要加在header区，不能放在外部CSS文件里