I'm having a similar type of layout issue.
I am trying to implement a chained ajax drop-down selector based on sample code from this site
http://demo.tutorialzine.com/2011/11/chained-ajax-selects-jquery/ with the intended goal of expanding the existing Search and Advanced Search block capabilities to be able to offer the user the ability to drill-down categories (products, ads and articles) when performing a search.
I've taken this sample code and put it into a custom block - minus the reference to 'assets/css/styles.css' in the index.html reference sample (code attached)
Problem is that the drop-down items are appearing behind the bottom edge of the custom block area.
I've played with several z-index settings in the style sheet , but to no avail.
Any suggestions
I've included a screen shot of whats going on as well as the reference sites original code (remove the .txt from the end).
Thanks in advance.