String issues (mainly)

There are some thing to be fixed:

There is (at least one) tag <i> which must be replaced by <em> for XHTML compatibility.

There are misspellings in

- The name of the customer to serch for ("serch" instead of "search")
- Allow the user to change there address during checkout ("there" instead of "their")
- Enter the id's of the products that you which to add to the invoice (which instead of wish?)

There's something missing in " To remove this content type then delete it !url"