Should I have a column for every data type or 1 column that stores everything I have a database table that currently looks like this:

PageField
-Id (Int, PK)
-FieldType (String) Can be Text, Decimal, Integer or Bit
-Value (This stores the value regardless of the FieldType, so it is not strongly typed)


Should I remove the Value column and replace it with 4 separate columns TextValue, DecimalValue, IntegerValue, and BitValue?

The data type would be set to what is relevant. This would mean in every row 3 of these 4 columns would be NULL.
This question (in various guises) crops up regularly. This type of "solution" is known as EAV (Entity-Attribute-Value) and is not a good idea. Take a look here or here for tips (or links to tips) on the problems it can cause and how to properly leverage the data types that your RDBMS offers.

Not using the correct data type is a sure fire way to confuse the 
query optimiser and slow your system down. Joe Celko is a world renowned expert in all matters SQL and his opinions merit attention. 

The fact that he uses the acronym "MUCK" (*) to describe this system should tell you all you need to know :-)

(*) Massively Unified Code Key