Currently Being ModeratedNov 7, 2012 8:04 PM (in response to cem1969)
How are you exporting? If dragging, you are only dragging the Preview and not the actual version.
Choose an image, click on File/Export and then select the size file you want to export.
Currently Being ModeratedNov 8, 2012 12:20 AM (in response to cem1969)
You may want to check the "original size" preset you are using, if it has been modified accidentally.
When exporting, first select the preset you want to use, for example (JPEG Original size), then change the selector to "Edit".
I the Image Export panel that opens check the value of the "Size to" pop-up, if it is still set to "original size" and check the quality slider, if the jpeg quality is sufficient. If it is set to a value below "8" you are likely to see jpeg artefacts.
Currently Being ModeratedNov 8, 2012 7:20 AM (in response to cem1969)
Are you actually seeing a degradation of the image in PS or are you only seeing that the DPI is 72?
The DPI of an image only matters when you print it out, it has no bearing on the quality of the image as viewed on the monitor.
If you are really concerned about this either pick a preset that has a higher DPI or set it to what you want in the DPI box of the export preset window. (just below the Size To: box in the screen shot Léonie supplied above,)