Why do I see strange symbols mixed with text in some email attachments?

Joseph,

Your problem description leads me to suspect font problems.

According to Kurt Lang...Helvetica Fractions is a known source of many font issues. Kurt Lang also has an excellent treatise called Font Management in Mac OS X Tiger and Panther.

;~)

In emails received from certain persons/companies
which are read using Safari/Yahoo mail, frequently I
have weird symbols interspersed with normal text. A
common occurrence is that an apostrophe (') is
replaced with â€. Why is this happening, and how can
I fix it?

This is probably the result of a text being composed with "smart" punctuation and being read with the wrong encoding. To get correct display, you can try to change the encoding to UTF-8 or another "Western" variety via the View > Text Encoding menu of the browser or the Encoding button found in the Open dialogue of TextEdit in Plain Text mode.

PS A curly quote apostrophe encoded as UTF-8 is represented by the bytes E2 80 99. If these bytes are read instead as if they were encoded as Latin-1, they will display as †or possibly as ’. So setting the browser to UTF-8 should make the character display correctly.