blitz ratings often lower than standard ratings

does anyone know why many people's (including my) blitz rating is lower than their standard rating? like -150.

The blitz and standard ratings are not related to each other.  They are measuring the relative performance of two substantially different groups of players.

Ratings are not absolute, like the temperature at which water freezes or something like that. 

Plus, chess.com has "adjusted" the standard ratings in the past, awarding hundreds of points to higher rated players because there were some accomplished players whose ratings were considered too low. (Read about it: Standard Ratings Boost )

hardly anyone plays standard so our rating will be higher in standard but everyone plays blitz so it will be more accurate to your real skill in chess

Cheating has nothing to do with it.  My rating for blitz is about 200 points lower and I am not a cheater!  When I used to play in USCF tournaments my rating was in the 1700's - my blitz rating is barely 1500.  notmtwain's comment above is probably the real reason for the difference.

Because amateurs suck at blitz? I know I do!

Because of the extra time?

Contrary to what many people think, ratings do not directly measure skill at chess.

Ratings are based on a statistical analysis that provides an estimate of a player's skill relative to the other players in the group based on a players results within that group. (More accurately, rating differences are designed to measure the odds of one player defeating another.)

• Blitz ratings are based on results vs other players playing blitz.
• Standard ratings are based on results vs other players playing standard.
• Correspondence (a.k.a. "turn-based", "online", "daily") ratings are based on results vs other players playing correspondence.

This says nothing about the quality of play. In general, among players of equivalent ratings, I would expect the quality of play to be better with the longer time control.

Some players, however, adapt better to some time controls than others. Players who see and caculate rapidly will excel at blitz, thereby achieving a higher rating than might be expected based on results at a longer time control. But another player who is terrible at blitz could win at correspondence against the blitz player because he or she is capable, using the available time, of analysing deeper into the game.

In the end, ratings are no more or less than estimates. Their usefulness is to give us an idea of how we stand relative to other players and when ratings rise (or fall) it gives us an idea of whether or not we are making progress.

As always, "your mileage may vary ... "