diff --git a/src/allmydata/web/welcome.xhtml b/src/allmydata/web/welcome.xhtml
index 1cb99d8b5..e3b8350f8 100644
--- a/src/allmydata/web/welcome.xhtml
+++ b/src/allmydata/web/welcome.xhtml
@@ -77,7 +77,7 @@
 
                 <label for="upload-sdmf" class="radio">
                   <input type="radio" id="upload-sdmf" value="sdmf" name="format" />
-                  SDMF
+                  <acronym title="Small Distributed Mutable Files">SDMF</acronym>
                 </label>
 
                 <label for="upload-mdmf" class="radio">
@@ -95,7 +95,7 @@
               <form action="uri" method="post" enctype="multipart/form-data">
                 <label for="mkdir-sdmf" class="radio"> 
                   <input type="radio" checked="checked" id="mkdir-sdmf" value="sdmf" name="format" />
-                  SDMF
+                  <acronym title="Small Distributed Mutable Files">SDMF</acronym>
                 </label>
 
                 <label for="mkdir-mdmf" class="radio">