Hi community,
I have no idea of code and Apex but I managed to create a pop-up alert message when a field is not populated:

<apex:page standardController="Account" rendered="{!Account.InvoiceContactRef__c=null}"> <script type ="text/javascript"> { window.alert("ACTION MESSAGE TEST"); } </script> </apex:page>

However, I have to extend the code:
 
I need a bigger and colorfull pop-up alert - lets say for example red.
 
How can I adjust the pixel size of the pop-up + size of font and how can I set the background color?
 
Thanks,
Felix
 

I need some assistance with a popup alert I created for one of my case record types.  I want the alert to fire when a custom field (Wire to) is populated only.  What is currently happening is the alert is popping at every edit of the record, even when this field is not populated.  

I need the alert to validate when the Wire to field is not null and then display the message.