Ok - you put the slider call function directly into the html document. In this case you don't need js/custom.js (just remove the file reference). Maybe you're using the jQuery noConflict mode . in this case replace:
$('#frontpage-slider').aviaSlider({
blockSize: {height: 80, width:80},
transition: 'slide',
display: 'all',
transitionOrder: ['diagonaltop', 'diagonalbottom','topleft', 'bottomright', 'random']
});
with:
jQuery(document).ready(function(){
jQuery('#frontpage-slider').aviaSlider({
blockSize: {height: 80, width:80},
transition: 'slide',
display: 'all',
transitionOrder: ['diagonaltop', 'diagonalbottom','topleft', 'bottomright', 'random']
});
});
In addition you load the jQuery libary several times which probably breaks all jQuery functions. I'd remove following two lines too:
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js"></script>
<script>!window.jQuery && document.write(unescape('%3Cscript src="js/libs/jquery-1.5.1.min.js"%3E%3C/script%3E'))</script>