diff --git a/pom.xml b/pom.xml
index 512958f5ede..2660302dce6 100644
--- a/pom.xml
+++ b/pom.xml
@@ -199,7 +199,7 @@
 		<maven-source-plugin.version>3.2.1</maven-source-plugin.version>
 		<maven-toolchains-plugin.version>3.1.0</maven-toolchains-plugin.version>
 		<maven-war-plugin.version>3.3.2</maven-war-plugin.version>
-		<yuicompressor-maven-plugin.version>1.5.1</yuicompressor-maven-plugin.version>
+		<resources-optimizer-maven-plugin.version>2.4.1</resources-optimizer-maven-plugin.version>
 
 		<osgi.dynamicimport.package />
 		<osgi.export.package>*</osgi.export.package>
@@ -876,24 +876,6 @@
 						]]></signatures>
 					</configuration>
 				</plugin>
-				<plugin>
-					<groupId>net.alchim31.maven</groupId>
-					<artifactId>yuicompressor-maven-plugin</artifactId>
-					<version>${yuicompressor-maven-plugin.version}</version>
-					<configuration>
-						<statistics>true</statistics>
-						<jswarn>false</jswarn>
-						<suffix>.min</suffix>
-						<outputDirectory>${project.build.directory}/generated-res</outputDirectory>
-					</configuration>
-					<executions>
-						<execution>
-							<goals>
-								<goal>compress</goal>
-							</goals>
-						</execution>
-					</executions>
-				</plugin>
 				<plugin>
 					<groupId>org.apache.felix</groupId>
 					<artifactId>maven-bundle-plugin</artifactId>
@@ -1205,11 +1187,11 @@
 							<pluginExecutions>
 								<pluginExecution>
 									<pluginExecutionFilter>
-										<groupId>net.alchim31.maven</groupId>
-										<artifactId>yuicompressor-maven-plugin</artifactId>
+										<groupId>org.primefaces.extensions</groupId>
+										<artifactId>resources-optimizer-maven-plugin</artifactId>
 										<versionRange>[1.3.0,)</versionRange>
 										<goals>
-											<goal>compress</goal>
+											<goal>optimize</goal>
 										</goals>
 									</pluginExecutionFilter>
 									<action>
@@ -1273,6 +1255,30 @@
 						</lifecycleMappingMetadata>
 					</configuration>
 				</plugin>
+				<plugin>
+					<groupId>org.primefaces.extensions</groupId>
+					<artifactId>resources-optimizer-maven-plugin</artifactId>
+					<version>${resources-optimizer-maven-plugin.version}</version>
+					<configuration>
+						<suffix>.min</suffix>
+						<inputDir>${project.build.directory}/classes</inputDir>
+						<useDataUri>false</useDataUri>
+						<resourcesSets>
+							<resourcesSet>
+								<excludes>
+									<exclude>**/jquery*.js</exclude>
+								</excludes>
+							</resourcesSet>
+						</resourcesSets>
+					</configuration>
+					<executions>
+						<execution>
+							<goals>
+								<goal>optimize</goal>
+							</goals>
+						</execution>
+					</executions>
+				</plugin>
 			</plugins>
 		</pluginManagement>
 	</build>
diff --git a/wicket-core/pom.xml b/wicket-core/pom.xml
index 7a4561643d5..bfb2204150f 100644
--- a/wicket-core/pom.xml
+++ b/wicket-core/pom.xml
@@ -28,11 +28,11 @@
 	<name>Wicket Core</name>
 	<description>
 		Wicket is a Java web application framework that takes simplicity,
-		separation of concerns and ease of development to a whole new level. 
-		Wicket pages can be mocked up, previewed and later revised using 
-		standard WYSIWYG HTML design tools. Dynamic content processing and 
-		form handling is all handled in Java code using a first-class 
-		component model backed by POJO data beans that can easily be 
+		separation of concerns and ease of development to a whole new level.
+		Wicket pages can be mocked up, previewed and later revised using
+		standard WYSIWYG HTML design tools. Dynamic content processing and
+		form handling is all handled in Java code using a first-class
+		component model backed by POJO data beans that can easily be
 		persisted using your favorite technology.
 	</description>
         <properties>
@@ -142,7 +142,7 @@ org.apache.wicket.util.template;-noimport:=true,
 org.apache.wicket.util.tester;-noimport:=true,
 org.apache.wicket.validation;-noimport:=true,
 org.apache.wicket.validation.validator;-noimport:=true
- 		</osgi.export.package> 
+ 		</osgi.export.package>
                 <osgi.import.package>!java*,!kotlin*,!sun.nio.ch,!com.sun.crypto.provider,org.slf4j*;version="[1.7,3)",javax.servlet,javax.servlet.http,*</osgi.import.package>
         </properties>
 	<dependencies>
@@ -196,23 +196,10 @@ org.apache.wicket.validation.validator;-noimport:=true
 		</dependency>
 	</dependencies>
 	<build>
-		<pluginManagement>
-			<plugins>
-				<plugin>
-					<groupId>net.alchim31.maven</groupId>
-					<artifactId>yuicompressor-maven-plugin</artifactId>
-					<configuration>
-						<excludes>
-							<exclude>**/jquery*.js</exclude>
-						</excludes>
-					</configuration>
-				</plugin>
-			</plugins>
-		</pluginManagement>
 		<plugins>
 			<plugin>
-				<groupId>net.alchim31.maven</groupId>
-				<artifactId>yuicompressor-maven-plugin</artifactId>
+				<groupId>org.primefaces.extensions</groupId>
+				<artifactId>resources-optimizer-maven-plugin</artifactId>
 			</plugin>
 		</plugins>
 	</build>
diff --git a/wicket-extensions/pom.xml b/wicket-extensions/pom.xml
index 5877047162c..668ea44c560 100644
--- a/wicket-extensions/pom.xml
+++ b/wicket-extensions/pom.xml
@@ -45,8 +45,8 @@
 	<build>
 		<plugins>
 			<plugin>
-				<groupId>net.alchim31.maven</groupId>
-				<artifactId>yuicompressor-maven-plugin</artifactId>
+				<groupId>org.primefaces.extensions</groupId>
+				<artifactId>resources-optimizer-maven-plugin</artifactId>
 			</plugin>
 		</plugins>
 	</build>
diff --git a/wicket-extensions/src/main/java/org/apache/wicket/extensions/markup/html/repeater/tree/theme/windows/theme.css b/wicket-extensions/src/main/java/org/apache/wicket/extensions/markup/html/repeater/tree/theme/windows/theme.css
index fa4b9014d99..b86245f1094 100644
--- a/wicket-extensions/src/main/java/org/apache/wicket/extensions/markup/html/repeater/tree/theme/windows/theme.css
+++ b/wicket-extensions/src/main/java/org/apache/wicket/extensions/markup/html/repeater/tree/theme/windows/theme.css
@@ -38,7 +38,7 @@ html[dir="rtl"] .tree-theme-windows div.tree-subtree {
 
 html[dir="rtl"] .tree-theme-windows div.tree-branch-mid {
   background-image: url(tree-rtl.gif);
-  background-position-x: calc(100%/* to skip */ +/* minimizer */ 54px);
+  background-position-x: calc(100% + 54px);
 }
 
 .tree-theme-windows div.tree-branch-last {