Disclaimer: This is a tip I received from tech support that my designer asked, and I'm simply passing it on to the forums. If you want to know why I'm doing this, read here:
http://forum.x-cart.com/showthread.php?t=42824. I'm not a web designer/developer, and I don't know anything about programming the back-end of X-Cart. My version of X-Cart is 4.1.10, so this tip may not work if you use a different version. If you have any questions about this tip, I can't answer them, but reply anyway and hopefully someone more knowledgeable will respond.
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You should modify the "<xcart_dir>/skin1/customer/main/subcategories.tpl" file using the instruction below:
1) Find the following code:
{capture name=dialog}
{assign var="tmp" value="0"}
and replace it with this one:
{*
{capture name=dialog}
{assign var="tmp" value="0"}
2) Find the following code:
{/capture}
{include file="dialog.tpl" title=$current_category.category content=$smarty.capture.dialog extra='width="100%"'}
and replace it with this one:
{/capture}
{include file="dialog.tpl" title=$current_category.category content=$smarty.capture.dialog extra='width="100%"'}
*}