#data
<button>1</foo>
#errors
#document
| <html>
|   <head>
|   <body>
|     <button>
|       "1"

#data
<foo>1<p>2</foo>
#errors
#document
| <html>
|   <head>
|   <body>
|     <foo>
|       "1"
|       <p>
|         "2"

#data
<dd>1</foo>
#errors
#document
| <html>
|   <head>
|   <body>
|     <dd>
|       "1"

#data
<foo>1<dd>2</foo>
#errors
#document
| <html>
|   <head>
|   <body>
|     <foo>
|       "1"
|       <dd>
|         "2"