I tried to add validation on sharepoint 2010 list to validate 4 columns but, the length of this validation is greater than length of text box to write the formula. Is there any way to expand this text box or what i can do even i need all cases in this validation???
As far as extending validation text box length for formula, I know of no way.
If the validation is column specific then you can add validation to each column separately. You only need to do it at the list level when the validation is related to more than one column.