[Anuj]

Yes, because in workflow we can not define   which workflow fire first ,

If we have more than one workflow Rules on a single object than

workflow which has field update action fire first after that there is no sequence which one  Fire ,so this may affect other workflow

[Anuj]

There are following  many methods for HttpRequest. All are instance methods.

Http http = new Http();

HttpRequest req = new HttpRequest();
req.setEndpoint('http://www.xyz.com');
req.setMethod('GET');

[Anuj]

If you have to Create Roll-Up Summary field in the parent object, then use Master-Detail Relationship,

If a record on the master object is deleted, all its related detail records are deleted as well.

If  you don't want both the Objects are  Completely dependent on each other then use Look-Up Relationship because it doesn't follow Cascade delete.

[Anuj]

four Types of Page Layouts in Salesforce

1- Page layouts

2- Mini Page layouts

3- Compact layouts

4- Search layouts