If you want to change dimensions of thumbnails( auto read more thumbnails), follow these simpe steps.
Auto Read More Thumbnails
Now go to "Design" --> "Edit HTML". (if you are using Blogger new interface go to "Template" --> "Edit HTML").
Click on "Expand Widget Templates".
Find this (some parts of the code can be different,according to your template.):
<script type='text/javascript'> summary_noimg = 600; summary_img = 500; img_thumb_height = 150; img_thumb_width = 200; </script>
Look at the image:
To Change Thumbnail Sizes Find This
To change width, change the value of img_thumb_width.
To change height, change the value of img_thumb_height.
For example I change thumbnail width as 300px and height as 200px. Now code should be:
<script type='text/javascript'> summary_noimg = 600; summary_img = 500; img_thumb_height = 200; img_thumb_width = 300; </script>
save the template. refresh your site.
Width and Height of Thumbnail Has Changed