Inanimate het, hem (it), and ze (them) are the only personal pronouns that turn into pronominal adverbs when preceded by a preposition.
The same goes for unmarked, singular ze (her), which the Flemish use for singular inanimate feminine nouns. In Dutch, you would use hem as they do not distinguish between feminine and masculine nouns.
| preposition + het
| 
| er+preposition
|
| preposition + inanimate hem
|
| preposition + inanimate ze
|
Note that this only applies to the pronoun het, not to the article. The examples below will illustrate the idea.
Examples of het turning into er
| Hij wacht op het rapport.
| He is waiting for the report.
|
Hij wacht erop.
Not: Hij wacht op het.
| He is waiting for it.
|
| Het staat op het internet.
| It is ('stands') on the internet.
|
Het staat erop.
Not: het staat op het.
| It is on it.
|
Examples of hem turning into er
| Hij wacht op de trein.
| He is waiting for the train.
|
Hij wacht erop.
Not: Hij wacht op hem.
| He is waiting for it.
|
| Het staat op de voorpagina.
| It is ('stands') on the front page.
|
Het staat erop.
Not: het staat op hem.
| It is on it.
|
Flemish: Singular ze (her) turning into 'er'
In Flanders, we would use the feminine pronoun 'ze' instead of 'hem' because 'voorpagina' is a feminine noun. However, because it refers to an inanimate object, 'ze' also turns into 'er'. Thus, for Flemish students, the last line in the above example should read: "Not: het staat op ze."
Examples of ze (them) turning into er
Inanimate ze (them) undergoes the same treatment:
| Hij wacht op de rapporten.
| He is waiting for the reports.
|
Hij wacht erop.
Not: Hij wacht op ze.
| He is waiting for them.
|
| Het staat in de kranten.
| It is in the newspapers.
|
Het staat erin.
Not: Het staat in ze.
| It is in them.
|
Recall that this only applies to inanimate ze. When it refers to persons, we do not replace it by er.
Questions? 
