how to perform Image blurring using fspecial function?

I have been doing the following to blur an image using fspecial function:-

img = imread('cell.jpg'); h = fspecial('gaussian',size(img), 1.0); g = imfilter(img, h);

but the following error is being encountered:-

??? Error using ==> fspecial>ParseInputs at 356 FSPECIAL: size(N) should be less than or equal 2.

Error in ==> fspecial at 97 [type, p2, p3] = ParseInputs(varargin{:});

Plz guide me how to define the hsize for the filter in order to work upon an image of 600 X 505..... Thank you.