apex code - How to turn off error messages in visualforce? -

i have visualforce page has 3 functionalities, hence has 3 'public pagereference' subroutines, called when action happens in page [i.e. button]

one of functionalities requires user input [i.e. inputtext], main apex code has variable declaration input:

public string userinput { get; set; } 

since each task not related, when hit button on other 2 functionalities, visualforce error, because inputtext object has no user input,

how can prevent happening,

another way solve this, how turn off visualforce error messages? can error handling apex, looking @ debug log file, error in visualforce not apex,

thanks

if don't want fire validation can use immediate = true attribute on commandbutton/commandlink bypass validation. - isn't optimal in opinion

if want submit part of page , still fire validation have @ actionregion. should allow wrap particular region action call. best purpose.

sorry don't have time post full examples should point in right direction :)