diff --git a/parameters/ant-parameters-details.dita b/parameters/ant-parameters-details.dita
index 1badd09de..271868ac0 100644
--- a/parameters/ant-parameters-details.dita
+++ b/parameters/ant-parameters-details.dita
@@ -223,8 +223,7 @@
             </pt>
             <pd conaction="mark" conref="parameters-base.dita#base/dita.input.valfile.desc"/>
             <pd conaction="pushafter">
-              <note type="notice">This parameter is deprecated in favor of the <parmname>args.filter</parmname>
-                parameter.</note>
+              <note type="notice">This parameter is deprecated; use <parmname>args.filter</parmname> instead.</note>
             </pd>
           </plentry>
           <plentry id="filter-stage">
@@ -522,8 +521,7 @@
             <pd conaction="pushafter">
               <div id="args.hide.parent.link.details">
                 <ph audience="xslt-customizer">Corresponds to the XSLT parameter <parmname>NOPARENTLINK</parmname>.</ph>
-                <note type="notice">This parameter is deprecated in favor of the <parmname>args.rellinks</parmname>
-                  parameter.</note>
+                <note type="notice">This parameter is deprecated; use <parmname>args.rellinks</parmname> instead.</note>
               </div></pd>
           </plentry>
           <plentry id="args.outext">
@@ -713,15 +711,21 @@
                 <xref keyref="jelovirt-on-pdf2-i18n"/>.</note>
             </pd>
           </plentry>
-          <plentry id="outputFile.base">
+          <plentry id="outputFile.base" importance="deprecated">
             <pt>
               <parmname>outputFile.base</parmname>
+              <ph>
+                <indexterm>deprecated features
+                  <indexterm><parmname>outputFile.base</parmname></indexterm></indexterm></ph>
             </pt>
             <pd conaction="mark" conref="parameters-pdf.dita#pdf/outputFile.base.desc"/>
             <pd conaction="pushafter">By default, the PDF file uses the base filename of the input
                 <filepath>.ditamap</filepath> file.
               <indexterm>DITA maps
-                <indexterm>PDF file name</indexterm></indexterm></pd>
+                <indexterm>PDF file name</indexterm></indexterm>
+              <note type="notice">This parameter is deprecated since DITA-OT 3.0; use
+                <parmname>args.output.base</parmname> instead.</note>
+            </pd>
           </plentry>
           <plentry id="pdf.formatter">
             <pt>
@@ -747,9 +751,10 @@
             </pt>
             <pd conaction="mark" conref="parameters-pdf.dita#pdf/publish.required.cleanup.desc"/>
             <pd conaction="pushafter">The default value is the value of the <parmname>args.draft</parmname> parameter.
-                <ph audience="xslt-customizer">Corresponds to the XSLT parameter
-                  <parmname>publishRequiredCleanup</parmname>.</ph><note type="notice">This parameter is deprecated in
-                favor of the <parmname>args.draft</parmname> parameter.</note></pd>
+              <ph audience="xslt-customizer">Corresponds to the XSLT parameter
+                  <parmname>publishRequiredCleanup</parmname>.</ph>
+              <note type="notice">This parameter is deprecated; use
+                  <parmname>args.draft</parmname> instead.</note></pd>
           </plentry>
         </parml>
       </section>
diff --git a/resources/dita-ot-doc.css b/resources/dita-ot-doc.css
index 6e1ae32e8..c2d91668b 100644
--- a/resources/dita-ot-doc.css
+++ b/resources/dita-ot-doc.css
@@ -789,6 +789,24 @@ pre code {
   font-size: 0.8125rem;
 }
 
+/* Mark deprecated elements */
+
+[data-importance='deprecated'],
+[data-importance='deprecated'] + dd,
+[data-importance='deprecated'] .parmname {
+  color: var(--code-color);
+}
+
+dt[data-importance='deprecated'] .parmname::after {
+  border-radius: 0.25rem;
+  content: 'DEPRECATED';
+  font-size: 75%;
+  margin-left: 0.5em;
+  padding: 0.25em 0.4em;
+  background-color: var(--code-color);
+  color: var(--secondary-bg);
+}
+
 /****************************************
 Headings
 ****************************************/
diff --git a/resources/html.ditaval b/resources/html.ditaval
index d6c511351..834cc486f 100644
--- a/resources/html.ditaval
+++ b/resources/html.ditaval
@@ -3,4 +3,5 @@
 <val>
   <prop action="include" att="deliveryTarget" val="html"/>
   <prop action="exclude" att="deliveryTarget" val="pdf"/>
+  <prop action="passthrough" att="importance"/>
 </val>
diff --git a/resources/pdf.ditaval b/resources/pdf.ditaval
index 82a036248..372b0a019 100644
--- a/resources/pdf.ditaval
+++ b/resources/pdf.ditaval
@@ -3,4 +3,5 @@
 <val>
   <prop action="exclude" att="deliveryTarget" val="html"/>
   <prop action="include" att="deliveryTarget" val="pdf"/>
+  <prop action="passthrough" att="importance"/>
 </val>
diff --git a/resources/site.ditaval b/resources/site.ditaval
index b620aa17d..5a0db8256 100644
--- a/resources/site.ditaval
+++ b/resources/site.ditaval
@@ -3,5 +3,6 @@
 <val>
   <prop action="include" att="deliveryTarget" val="html"/>
   <prop action="exclude" att="deliveryTarget" val="pdf"/>
+  <prop action="passthrough" att="importance"/>
   <prop action="passthrough" att="platform"/>
 </val>