String comparison problem.

Dear All,
           I have some problem with string comparison. I use 
postgresql 8.3.1,UTF8 encoding, on CentOS 5.5. Why dose the result of  
SQL statement :  "select '1.1' < '101';" is false but "select 
'1.1'::bytea < '101'::bytea;" is ture?


mis=# select '.' < '0';
?column?
----------
t
(1 row)



mis=# select '1.' < '10';
?column?
----------
t
(1 row)



mis=# select '1.1' < '101';
?column?
----------
f
(1 row)


mis=# select '1.1'::text < '101'::text;
?column?
----------
f
(1 row)


mis=# select '1.1'::bytea < '101'::bytea;
?column?
----------
t
(1 row)


Thank you very much.