One of my project's doesn't compile, and therefore there is no target/docs directory for that project. the multiproject:site target fails because the target/docs project doesn't exist:

C:\maven\sources\maven>maven -e multiproject:site

...

[echo] Now building reactor projects: [CS Common, CS Log Service, , CS Log Service, Mail Common, Mail Purge, Mail
[copy] Copying 329 files to C:\maven\sources\maven\target\docs\multiproject\cs-common
[copy] Copying 109 files to C:\maven\sources\maven\target\docs\multiproject\logservice
[copy] Copying 109 files to C:\maven\sources\maven\target\docs\multiproject\cs-sources
[copy] Copying 200 files to C:\maven\sources\maven\target\docs\multiproject\cs-logservice
[copy] Copying 206 files to C:\maven\sources\maven\target\docs\multiproject\cs-mailpim-common

BUILD FAILED
C:\maven\sources\cs-mailpim-purge\target\docs not found.
at org.apache.tools.ant.types.AbstractFileSet.getDirectoryScanner(AbstractFileSet.java:369)
at org.apache.tools.ant.taskdefs.Copy.execute(Copy.java:355)
at org.apache.tools.ant.Task.perform(Task.java:341)
at org.apache.commons.jelly.tags.ant.AntTag.doTag(AntTag.java:232)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:279)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:135)
at org.apache.commons.jelly.TagSupport.invokeBody(TagSupport.java:233)
at org.apache.commons.jelly.tags.core.ForEachTag.doTag(ForEachTag.java:145)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:279)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:135)
at org.apache.commons.jelly.TagSupport.invokeBody(TagSupport.java:233)
at org.apache.commons.jelly.tags.core.IfTag.doTag(IfTag.java:88)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:279)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:135)
at org.apache.maven.jelly.tags.werkz.MavenGoalTag.runBodyTag(MavenGoalTag.java:79)
at org.apache.maven.jelly.tags.werkz.MavenGoalTag$MavenGoalAction.performAction(MavenGoalTag.java:110)
at com.werken.werkz.Goal.fire(Goal.java:639)
at com.werken.werkz.Goal.attain(Goal.java:575)
at com.werken.werkz.WerkzProject.attainGoal(WerkzProject.java:193)
at org.apache.maven.plugin.PluginManager.attainGoals(PluginManager.java:610)
at org.apache.maven.MavenSession.attainGoals(MavenSession.java:266)
at org.apache.maven.cli.App.doMain(App.java:485)
at org.apache.maven.cli.App.main(App.java:1214)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at com.werken.forehead.Forehead.run(Forehead.java:551)
at com.werken.forehead.Forehead.main(Forehead.java:581)
File...... C:\Documents and Settings\mmattox\.maven\plugins\maven-multiproject-plugin-1.3\plugin.jelly
Element... copy
Line...... 118
Column.... 36
C:\maven\sources\cs-mailpim-purge\target\docs not found.
Total time: 13 minutes 17 seconds
Finished at: Thu May 27 16:40:03 CEST 2004