random header pic, how? Options

[lishashima]

i want to make a header which the pic random on refreshing it

the size and the location of the pic is in my xanga

M Y X A N G A

how can i do?

<!-- begin code provided by createblog.com --><br /><!-- begin code provided by createblog.com --><br /><script LANGUAGE="JavaScript"><br /><br /><!-- Begin<br />// Set up the image files to be used.<br />var theImages = new Array() // do not change this<br />// To add more image files, continue with the<br />// pattern below, adding to the array.<br /><br />theImages[0] = 'INSERT IMAGE URL HERE'<br />theImages[1] = 'INSERT IMAGE URL HERE'<br />theImages[2] = 'INSERT IMAGE URL HERE'<br />theImages[3] = 'INSERT IMAGE URL HERE'<br />theImages[4] = 'INSERT IMAGE URL HERE'<br /><br />// do not edit anything below this line<br /><br />var j = 0<br />var p = theImages.length;<br />var preBuffer = new Array()<br />for (i = 0; i < p; i++){<br />   preBuffer[i] = new Image()<br />   preBuffer[i].src = theImages[i]<br />}<br />var whichImage = Math.round(Math.random()*(p-1));<br />function showImage(){<br />document.write('<img src="'+theImages[whichImage]+'">');<br />}<br /><br />//  End --><br /></script><br /><!-- end code provided by createblog.com --><br /><!-- end code provided by createblog.com -->

I tried the code above, but it is not working