Jaime Israel Ramírez Hernández:
I had the same issue and it took me a while to solve it. First I used a work around by adding referrence to jquery-ui.css (ex: jquery-ui-1.7.2.custom.css) in top_head.jsp /html/common/themse/top_head.jsp
<link type="text/css" href="/html/css/jquery-ui-1.7.2.custom.css" rel="stylesheet" />
I found it a dirty solution but it worked perfectly. Then I found a better solution which is as follows:
1- created css.jsp (or anything you want to name it.
2- added content of jquery-ui-1.7.2.custom.css to css.jsp
3- added the following xml elements to my <portlet> in my lifray-portlet-ext.xml
<header-portlet-css>/html/portlet/ext/personalization_wizard/css.jsp</header-portlet-css>
<add-default-resource>true</add-default-resource>
if anybody else has found better solutions, please post them.