fix image screen when uploading in wp post

[opensource]

hello

How do I make into css that my blog width is 700px
then my image upload is 900px width.

Basically I want when i upload the image in my blog post,
the 900px screen size is set into 700px width view screen.
Just like when uploading img in facebook, when you have
400px then the img screen will only displays 300px width
in the timeline.
How did they done that in css?
Are they using overflow:hidden ? I tried it but no luck.

 

[chrishirst]

Resize the image using server side code.

 

[opensource]

Thanks mate. Il try this one. Il get back and update.
And is there also other alternate way aside from this? Just a thought.

 

[Phreaddee]

#blogpostcontainer {width:700px;}
#blogpostcontainer img {max-width:100%;height:auto;}