That’s happening because the “#header” rule you added in your custom CSS is too big and covers up the link.
The best way to make RSS link clickable on your categories pages again would be to make the #header element fit to the header background image you added without any extra bottom padding (the padding is what’s covering up the link). Here is an example of how you can fix it based on your current custom CSS:
In the “#header” block, set the padding to zero:
padding:0;
In the “#pagenav” block, adjust the top value to move the menu back into place:
top:-60px;
Then add some padding back to the “#content” area to move the main content down after the spacing adjustments from above:
#content {
padding-top: 90px;
}
Adjust the numbers as necessary.